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  • 1.
    Adibekyan, V.
    et al.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, P-4150762 Oporto, Portugal..
    Delgado-Mena, E.
    Univ Porto, Inst Astrofis & Ciencias Espaco, CAUP, Rua Estrelas, P-4150762 Oporto, Portugal..
    Feltzing, S.
    Lund Observ, Dept Astron & Theoret Phys, Lund, Sweden..
    Gonzalez Hernandez, J. I.
    Inst Astrofis Canarias, Tenerife, Spain.;Univ La Laguna, Dept Astrofis, Tenerife, Spain..
    Hinkel, N. R.
    Arizona State Univ, Sch Earth & Space Explorat, Tempe, AZ USA.;Vanderbilt Univ, Dept Phys & Astron, Nashville, TN 37235 USA..
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Uppsala Univ, Dept Phys & Astron, Uppsala, Sweden..
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT, Australia..
    Beck, P. G.
    Univ Paris Diderot, Ctr Saclay, Lab AIM, CEA,DRF,CNRS,IRFU,SAp, Gif Sur Yvette, France..
    Deal, M.
    Univ Montpellier, CNRS, LUPM, UMR 5299, Montpellier, France.;CNRS, IRAP, Toulouse, France..
    Gustafsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. NORDITA, Stockholm, Sweden..
    Honda, S.
    Univ Hyogo, Ctr Astron, Nishi Harima Astron Observ, Sayo, Hyogo, Japan..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Max Planck Inst Astron, Heidelberg, Germany..
    Nissen, P. E.
    Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Aarhus C, Denmark..
    Spina, L.
    Univ Sao Paulo, Dept Astron IAG, Sao Paulo, Brazil..
    Sun-like stars unlike the Sun: Clues for chemical anomalies of cool stars2017In: Astronomical Notes - Astronomische Nachrichten, ISSN 0004-6337, E-ISSN 1521-3994, Vol. 338, no 4, p. 442-452Article in journal (Refereed)
    Abstract [en]

    We present a summary of the splinter session Sun-like stars unlike the Sun that was held on June 9, 2016, as part of the Cool Stars 19 conference (Uppsala, Sweden), in which the main limitations (in the theory and observations) in the derivation of very precise stellar parameters and chemical abundances of Sun-like stars were discussed. The most important and most debated processes that can produce chemical peculiarities in solar-type stars were outlined and discussed. Finally, in an open discussion between all the participants, we tried to identify new pathways and prospects toward future solutions of the currently open questions.

  • 2.
    Amarsi, A. M.
    et al.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Barklem, Paul S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Collet, R.
    Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 463, no 2, p. 1518-1533Article in journal (Refereed)
    Abstract [en]

    As one of the most important elements in astronomy, iron abundance determinations need to be as accurate as possible. We investigate the accuracy of spectroscopic iron abundance analyses using archetypal metal-poor stars. We perform detailed 3D non-LTE radiative transfer calculations based on 3D hydrodynamic STAGGER model atmospheres, and employ a new model atom that includes new quantum-mechanical neutral hydrogen collisional rate coefficients. With the exception of the red giant HD122563, we find that the 3D non-LTE models achieve Fe I/Fe II excitation and ionization balance as well as not having any trends with equivalent width to within modelling uncertainties of 0.05 dex, all without having to invoke any microturbulent broadening; for HD122563 we predict that the current best parallax-based surface gravity is overestimated by 0.5 dex. Using a 3D non-LTE analysis, we infer iron abundances from the 3D model atmospheres that are roughly 0.1 dex higher than corresponding abundances from 1D MARCS model atmospheres; these differences go in the same direction as the non-LTE effects themselves. We make available grids of departure coefficients, equivalent widths and abundance corrections, calculated on 1D MARCS model atmospheres and horizontally and temporally averaged 3D STAGGER model atmospheres.

  • 3.
    Amarsi, A. M.
    et al.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Nissen, P. E.
    Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia;ASTRO 3D, ARC Ctr Excellence All Sky Astrophys 3 Dimens, Sydney, NSW, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Barklem, Paul
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Carbon and oxygen in metal-poor halo stars2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 622, article id L4Article in journal (Refereed)
    Abstract [en]

    Carbon and oxygen are key tracers of the Galactic chemical evolution; in particular, a reported upturn in [C/O] towards decreasing [O/H] in metal-poor halo stars could be a signature of nucleosynthesis by massive Population III stars. We reanalyse carbon, oxygen, and iron abundances in 39 metal-poor turn-off stars. For the first time, we take into account 3D hydrodynamic effects together with departures from local thermodynamic equilibrium (LTE) when determining both the stellar parameters and the elemental abundances, by deriving effective temperatures from 3D non-LTE H beta profiles, surface gravities from Gaia parallaxes, iron abundances from 3D LTE Fe ii equivalent widths, and carbon and oxygen abundances from 3D non-LTE C-I and O-I equivalent widths. We find that [C/Fe] stays flat with [Fe/H], whereas [O/Fe] increases linearly up to 0.75 dex with decreasing [Fe/H] down to -3.0 dex. Therefore [C/O] monotonically decreases towards decreasing [C/H], in contrast to previous findings, mainly because the non-LTE e ff ects for O i at low [Fe/H] are weaker with our improved calculations.

  • 4.
    Amarsi, A. M.
    et al.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Nordlander, T.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia;ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia.
    Barklem, Paul
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Collet, R.
    Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Effective temperature determinations of late-type stars based on 3D non-LTE Balmer line formation2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 615, article id A139Article in journal (Refereed)
    Abstract [en]

    Hydrogen Balmer lines are commonly used as spectroscopic effective temperature diagnostics of late-type stars. However, reliable inferences require accurate model spectra, and the absolute accuracy of classical methods that are based on one-dimensional (1D) hydrostatic model atmospheres and local thermodynamic equilibrium (LTE) is still unclear. To investigate this, we carry out 3D non-LTE calculations for the Balmer lines, performed, for the first time, over an extensive grid of 3D hydrodynamic STAGGER model atmospheres. For H alpha, H beta, and H gamma we find significant 1D non-LTE versus 3D non-LTE differences (3D effects): the outer wings tend to be stronger in 3D models, particularly for H gamma, while the inner wings can be weaker in 3D models, particularly for H alpha. For H alpha, we also find significant 3D LTE versus 3D non-LTE differences (non-LTE effects): in warmer stars (T-eff approximate to 6500 K) the inner wings tend to be weaker in non-LTE models, while at lower effective temperatures (T-eff approximate to 4500 K) the inner wings can be stronger in non-LTE models; the non-LTE effects are more severe at lower metallicities. We test our 3D non-LTE models against observations of well-studied benchmark stars. For the Sun, we infer concordant effective temperatures from H alpha, H beta, and H gamma; however the value is too low by around 50 K which could signal residual modelling shortcomings. For other benchmark stars, our 3D non-LTE models generally reproduce the effective temperatures to within 1 sigma uncertainties. For H alpha, the absolute 3D effects and non-LTE effects can separately reach around 100 K, in terms of inferred effective temperatures. For metal-poor turn-off stars, 1D LTE models of H alpha can underestimate effective temperatures by around 150 K. Our 3D non-LTE model spectra are publicly available, and can be used for more reliable spectroscopic effective temperature determinations.

  • 5.
    Bensby, Thomas
    et al.
    Lund Observ, Dept Astron & Theoret Phys, Lund, Sweden.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Max Planck Inst Astron, Heidelberg, Germany.
    Exploring the production and depletion of lithium in the Milky Way stellar disk2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 615, article id A151Article in journal (Refereed)
    Abstract [en]

    Despite the recent availability of large samples of stars with high-precision Li abundances, there are many unanswered questions about the evolution of this unique element in the Galaxy and in the stars themselves. It is unclear which parameters and physical mechanisms govern Li depletion in late-type stars and if Galactic enrichment has proceeded differently in different stellar populations. With this study we aim to explore these questions further by mapping the evolution of Li with stellar mass, age, and effective temperature for Milky Way disk stars, linking the metal-poor and metal-rich regimes, and how Li differs in the thin and thick disks. We determine Li abundances for a well-studied sample of 714 F and G dwarf, turn-off, and subgiant stars in the solar neighbourhood. The analysis is based on line synthesis of the Li-7 line at 6707 angstrom in high-resolution and high-signal-to-noise ratio echelle spectra, obtained with the MIKE, FEROS, SOFIN, UVES, and FIES spectrographs. The presented Li abundances are corrected for non-LTE effects. Out of the sample of 714 stars, we are able to determine Li abundances for 394 stars and upper limits on the Li abundance for another 121 stars. Out of 36 stars that are listed as exoplanet host stars, 18 have well-determined Li abundances and 6 have Li upper limits. Our main finding is that there are no signatures of Li production in stars associated with the thick disk. Instead the Li abundance trend is decreasing with metallicity for these thick disk stars. Significant Li production is however seen in the thin disk, with a steady increase towards super-solar metallicities. At the highest metallicities, however, around [Fe/H] approximate to +0.3, we tentatively confirm the recent discovery that the Li abundances level out. Our finding contradicts the other recent studies that found that Li is also produced in the thick disk. We find that this is likely due to the alpha-enhancement criteria which those studies used to define their thick disk samples. By using the more robust age criteria, we are able to define a thick disk stellar sample that is much less contaminated by thin disk stars. Furthermore, we also tentatively confirm the age-Li correlation for solar twin stars, and we find that there is no correlation between Li abundance and whether the stars have detected exoplanets or not. The major conclusion that can be drawn from this study is that no significant Li production relative to the primordial abundance took place during the first few billion years of the Milky Way, an era coinciding with the formation and evolution of the thick disk. Significant Li enrichment then took place once long-lived low-mass stars (acting on a timescale longer than SNIa) had had time to contribute to the chemical enrichment of the interstellar medium.

  • 6. Bessell, Michael S.
    et al.
    Collet, Remo
    Keller, Stefan C.
    Frebel, Anna
    Heger, Alexander
    Casey, Andrew R.
    Masseron, Thomas
    Asplund, Martin
    Jacobson, Heather R.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Marino, Anna F.
    Norris, John E.
    Yong, David
    Da Costa, Gary
    Chan, Conrad
    Magic, Zazralt
    Schmidt, Brian
    Tisserand, Patrick
    Nucleosynthesis in a Primordial Supernova: Carbon and Oxygen Abundances in SMSS J031300.36-670839.32015In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 806, no 1, article id L16Article in journal (Refereed)
    Abstract [en]

    SMSS J031300.36-670839.3 (hereafter SM0313-6708) is a sub-giant halo star, with no detectable Fe lines and large overabundances of C and Mg relative to Ca. We obtained Very Large Telescope-Ultraviolet and Visual Echelle Spectrograph (UVES) spectra extending to 3060 angstrom showing strong OH A-X band lines enabling an oxygen abundance to be derived. The OH A-X band lines in SM0313-6708 are much stronger than the CH C-X band lines. Spectrum synthesis fits indicate an [O/C] ratio of 0.02 +/- 0.175. Our high signal-to-noise ratio UVES data also enabled us to lower the Fe abundance limit to [Fe/H](< 3D >,NLTE) < -7.52 (3 sigma). These data support our previous suggestion that the star formed from the iron-poor ejecta of a single massive star Population III supernova.

  • 7.
    Bland-Hawthorn, Joss
    et al.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia;Univ Calif Berkeley, Miller Inst, Berkeley, CA 94720 USA.
    Sharma, Sanjib
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia.
    Tepper-Garcia, Thor
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia.
    Binney, James
    Clarendon Lab, Rudolf Peierls Ctr Theoret Phys, Oxford OX1 3PU, England.
    Freeman, Ken C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Hayden, Michael R.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia.
    Kos, Janez
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.
    De Silva, Gayandhi M.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Macquarie Univ, Dept Phys & Astron, N Ryde, NSW 2109, Australia.
    Ellis, Simon
    Macquarie Univ, Dept Phys & Astron, N Ryde, NSW 2109, Australia.
    Lewis, Geraint F.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.
    Asplund, Martin
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Buder, Sven
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany;Heidelberg Univ, Int Max Planck Res Sch Astron & Cosm Phys, Heidelberg, Germany.
    Casey, Andrew R.
    Monash Univ, Monash Ctr Astrophys, Clayton, Vic 3800, Australia;Monash Univ, Sch Phys & Astron, Clayton, Vic 3800, Australia.
    D'Orazi, Valentina
    INAF Astron Observ Padova, I-36012 Asiago, Italy.
    Duong, Ly
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Khanna, Shourya
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia.
    Lin, Jane
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Martell, Sarah L.
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia;UNSW, Sch Phys, Sydney, NSW 2052, Australia.
    Ness, Melissa K.
    Columbia Univ, Dept Astron, Pupin Phys Labs, New York, NY 10027 USA;Flatiron Inst, Ctr Computat Astrophys, 162 Fifth Ave, New York, NY 10010 USA.
    Simpson, Jeffrey D.
    UNSW, Sch Phys, Sydney, NSW 2052, Australia.
    Zucker, Daniel B.
    Macquarie Univ, Dept Phys & Astron, N Ryde, NSW 2109, Australia.
    Zwitter, Tomaz
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Kafle, Prajwal R.
    Univ Western Australia, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia.
    Quillen, Alice C.
    Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA.
    Ting, Yuan-Sen
    Inst Adv Study, Olden Lane, Princeton, NJ 08540 USA;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA;Observ Carnegie Inst Washington, 813 Santa Barbara St, Pasadena, CA 91101 USA.
    Wyse, Rosemary F. G.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    The GALAH survey and Gaia DR2: dissecting the stellar disc's phase space by age, action, chemistry, and location2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 486, no 1, p. 1167-1191Article in journal (Refereed)
    Abstract [en]

    We use the second data releases of the European Space Agency Gaia astrometric survey and the high-resolution Galactic Archaeology with HERMES (GALAH) spectroscopic survey to analyse the structure of our Galaxy's disc components. With GALAH, we separate the alpha-rich and alpha-poor discs (with respect to Fe), which are superposed in both position and velocity space, and examine their distributions in action space. We study the distribution of stars in the zV(z) phase plane, for both V-phi and V-R, and recover the remarkable 'phase spiral' discovered by Gaia. We identify the anticipated quadrupole signature in zV(z) of a tilted velocity ellipsoid for stars above and belowtheGalactic plane. By connecting ourwork with earlier studies, we show that the phase spiral is likely to extend well beyond the narrow solar neighbourhood cylinder in which it was found. The phase spiral is a signature of corrugated waves that propagate through the disc, and the associated non-equilibrium phase mixing. The radially asymmetric distribution of stars involved in the phase spiral reveals that the corrugation, which is mostly confined to the alpha-poor disc, grows in z-amplitude with increasing radius. We present new simulations of tidal disturbance of the Galactic disc by the Sagittarius (Sgr) dwarf. The effect on the zV(z) phase plane lasts greater than or similar to 2 Gyr, but a subsequent disc crossing wipes out the coherent structure. We find that the phase spiral was excited less than or similar to 0.5 Gyr ago by an object like Sgr with total mass similar to 3 x 10(10) M-circle dot (stripped down from similar to 5 x 10(10) M-circle dot when it first entered the halo) passing through the plane.

  • 8.
    Buder, S.
    et al.
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany;Heidelberg Univ, Int Max Planck Res Sch Astron & Cosm Phys, Heidelberg, Germany.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Ness, M. K.
    Columbia Univ, Dept Astron, Pupin Phys Labs, New York, NY 10027 USA;Flatiron Inst, Ctr Computat Astrophys, 162 Fifth Ave, New York, NY 10010 USA.
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Mt Stromlo Observ, Weston, ACT 2611, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia.
    Duong, L.
    Australian Natl Univ, Res Sch Astron & Astrophys, Mt Stromlo Observ, Weston, ACT 2611, Australia.
    Lin, J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Mt Stromlo Observ, Weston, ACT 2611, Australia.
    Kos, J.
    Univ Sydney, Sch Phys, A28, Sydney Inst Astron SIfA, Sydney, NSW 2006, Australia;Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Casagrande, L.
    Australian Natl Univ, Res Sch Astron & Astrophys, Mt Stromlo Observ, Weston, ACT 2611, Australia.
    Casey, A. R.
    Monash Univ, Sch Phys & Astron, Melbourne, Vic, Australia;Monash Univ, Fac Informat Technol, Melbourne, Vic, Australia.
    Bland-Hawthorn, J.
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Univ Sydney, Sch Phys, A28, Sydney Inst Astron SIfA, Sydney, NSW 2006, Australia;Univ Calif Berkeley, Miller Inst, Berkeley, CA 94720 USA.
    De Silva, G. M.
    Univ Sydney, Sch Phys, A28, Sydney Inst Astron SIfA, Sydney, NSW 2006, Australia;Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.
    D'Orazi, V
    Osserv Astron Padova, Ist Nazl Astrofis, Vicolo Osservatorio 5, I-35122 Padua, Italy.
    Freeman, K. C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Mt Stromlo Observ, Weston, ACT 2611, Australia.
    Martell, S. L.
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Schlesinger, K. J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Mt Stromlo Observ, Weston, ACT 2611, Australia.
    Sharma, S.
    Univ Sydney, Sch Phys, A28, Sydney Inst Astron SIfA, Sydney, NSW 2006, Australia.
    Simpson, J. D.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Zucker, D. B.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.
    Zwitter, T.
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Cotar, K.
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Dotter, A.
    Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA.
    Hayden, M. R.
    Univ Sydney, Sch Phys, A28, Sydney Inst Astron SIfA, Sydney, NSW 2006, Australia.
    Hyde, E. A.
    Western Sydney Univ, Locked Bag 1797, Penrith, NSW 2751, Australia.
    Kafle, P. R.
    Univ Western Australia, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia.
    Lewis, G. F.
    Univ Sydney, Sch Phys, A28, Sydney Inst Astron SIfA, Sydney, NSW 2006, Australia.
    Nataf, D. M.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    Nordlander, T.
    Australian Natl Univ, Res Sch Astron & Astrophys, Mt Stromlo Observ, Weston, ACT 2611, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia.
    Reid, W.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia;Western Sydney Univ, Locked Bag 1797, Penrith, NSW 2751, Australia.
    Rix, H-W
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Skuladottir, A.
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Stello, D.
    Univ Sydney, Sch Phys, A28, Sydney Inst Astron SIfA, Sydney, NSW 2006, Australia;Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia;Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, DK-8000 Aarhus C, Denmark.
    Ting, Y-S
    Inst Adv Study, Olden Lane, Princeton, NJ 08540 USA;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA;Observ Carnegie Inst Washington, 813 Santa Barbara St, Pasadena, CA 91101 USA.
    Traven, G.
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Wyse, R. F. G.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    The GALAH survey: An abundance, age, and kinematic inventory of the solar neighbourhood made with TGAS2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 624, article id A19Article in journal (Refereed)
    Abstract [en]

    The overlap between the spectroscopic Galactic Archaeology with HERMES (GALAH) survey and Gaia provides a high-dimensional chemodynamical space of unprecedented size. We present a first analysis of a subset of this overlap, of 7066 dwarf, turn-off, and subgiant stars. These stars have spectra from the GALAH survey and high parallax precision from the Gaia DR1 Tycho-Gaia Astrometric Solution. We investigate correlations between chemical compositions, ages, and kinematics for this sample. Stellar parameters and elemental abundances are derived from the GALAH spectra with the spectral synthesis code SPECTROSCOPY MADE EASY. We determine kinematics and dynamics, including action angles, from the Gaia astrometry and GALAH radial velocities. Stellar masses and ages are determined with Bayesian isochrone matching, using our derived stellar parameters and absolute magnitudes. We report measurements of Li, C, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, as well as Ba and we note that we have employed non-LTE calculations for Li, O, Al, and Fe. We show that the use of astrometric and photometric data improves the accuracy of the derived spectroscopic parameters, especially log g. Focusing our investigation on the correlations between stellar age, iron abundance [Fe/H], and mean alpha-enhancement [alpha/Fe] of the magnitude-selected sample, we recover the result that stars of the high-a sequence are typically older than stars in the low-a sequence, the latter spanning iron abundances of -0.7 < [Fe/H] < +0.5. While these two sequences become indistinguishable in [alpha/Fe] vs. [Fe/H] at the metal-rich regime, we find that age can be used to separate stars from the extended high-a and the low-a sequence even in this regime. When dissecting the sample by stellar age, we find that the old stars (>8 Gyr) have lower angular momenta L-z than the Sun, which implies that they are on eccentric orbits and originate from the inner disc. Contrary to some previous smaller scale studies we find a continuous evolution in the high-alpha-sequence up to super-solar [Fe/H] rather than a gap, which has been interpreted as a separate "high-alpha metal-rich" population. Stars in our sample that are younger than 10 Gyr, are mainly found on the low alpha-sequence and show a gradient in L-z from low [Fe/H] > (L-z > L-z,L-circle dot) towards higher [Fe/H] (L-z < L-z,L-circle dot), which implies that the stars at the ends of this sequence are likely not originating from the close solar vicinity.

  • 9.
    Buder, Sven
    et al.
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany;Heidelberg Univ, Int Max Planck Res Sch Astron & Cosm Phys, Heidelberg, Germany.
    Asplund, Martin
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Duong, Ly
    Kos, Janez
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Ness, Melissa K.
    Columbia Univ, Dept Astron, Pupin Phys Labs, New York, NY 10027 USA;Flatiron Inst, Ctr Computat Astrophys, 162 Fifth Ave, New York, NY 10010 USA.
    Sharma, Sanjib
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia.
    Bland-Hawthorn, Joss
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Univ Calif Berkeley, Miller Inst, Berkeley, CA 94720 USA.
    Casey, Andrew R.
    Monash Univ, Monash Ctr Astrophys, Clayton, Vic 3800, Australia;Monash Univ, Sch Phys & Astron, Clayton, Vic 3800, Australia.
    De Silva, Gayandhi M.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia;Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia.
    D'Orazi, Valentina
    Ist Nazl Astrofis, Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy.
    Freeman, Ken C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Lewis, Geraint F.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia.
    Lin, Jane
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Martell, Sarah L.
    UNSW, Sch Phys, Sydney, NSW 2052, Australia.
    Schlesinger, Katharine J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Simpson, Jeffrey D.
    Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia.
    Zucker, Daniel B.
    Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia;Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.
    Zwitter, Tomaz
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Amarsi, Anish M.
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Anguiano, Borja
    Univ Virginia, Dept Astron, Charlottesville, VA 22904 USA.
    Carollo, Daniela
    INAF, Astrophys Observ Turin, Turin, Italy.
    Casagrande, Luca
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Cotar, Klemen
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Cottrell, Peter L.
    Univ Canterbury, Sch Phys & Chem Sci, Christchurch, New Zealand;Monash Univ, Sch Phys & Astron, Clayton, Vic 3800, Australia.
    Da Costa, Gary
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Gao, Xudong D.
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Hayden, Michael R.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia.
    Horner, Jonathan
    Univ Southern Queensland, Toowoomba, Qld 4350, Australia.
    Ireland, Michael J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Kafle, Prajwal R.
    Univ Western Australia, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia.
    Munari, Ulisse
    INAF Astron Observ Padova, I-36012 Asiago, Italy.
    Nataf, David M.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    Nordlander, Thomas
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Stello, Dennis
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Sydney, NSW, Australia;Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, DK-8000 Aarhus C, Denmark;UNSW, Sch Phys, Sydney, NSW 2052, Australia.
    Ting, Yuan-Sen
    Observ Carnegie Inst Washington, 813 Santa Barbara St, Pasadena, CA 91101 USA;Inst Adv Study, Olden Lane, Princeton, NJ 08540 USA;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA.
    Traven, Gregor
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Watson, Fred
    Western Sydney Univ, Locked Bag 1797, Penrith, NSW 2751, Australia;Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia.
    Wittenmyer, Robert A.
    Univ Southern Queensland, Computat Engn & Sci Res Ctr, Toowoomba, Qld 4350, Australia.
    Wyse, Rosemary F. G.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    Yong, David
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Zinn, Joel C.
    Ohio State Univ, Dept Astron, 140 West 18th Ave, Columbus, OH 43210 USA.
    Zerjal, Marusa
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    The GALAH Survey: second data release2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 478, no 4, p. 4513-4552Article in journal (Refereed)
    Abstract [en]

    The Galactic Archaeology with HERMES (GALAH) survey is a large-scale stellar spectroscopic survey of the Milky Way, designed to deliver complementary chemical information to a large number of stars covered by the Gaia mission. We present the GALAH second public data release (GALAH DR2) containing 342 682 stars. For these stars, the GALAH collaboration provides stellar parameters and abundances for up to 23 elements to the community. Here we present the target selection, observation, data reduction, and detailed explanation of how the spectra were analysed to estimate stellar parameters and element abundances. For the stellar analysis, we have used a multistep approach. We use the physics-driven spectrum synthesis of Spectroscopy Made Easy (SME) to derive stellar labels (T-eff, log g, [Fe/H], [X/Fe], v(mic), vsin i, AKS) for a representative training set of stars. This information is then propagated to the whole sample with the data-driven method of The Cannon. Special care has been exercised in the spectral synthesis to only consider spectral lines that have reliable atomic input data and are little affected by blending lines. Departures from local thermodynamic equilibrium (LTE) are considered for several key elements, including Li, O, Na, Mg, Al, Si, and Fe, using 1D MARCS stellar atmosphere models. Validation tests including repeat observations, Gaia benchmark stars, open and globular clusters, and K2 asteroseismic targets lend confidence to our methods and results. Combining the GALAH DR2 catalogue with the kinematic information from Gaia will enable a wide range of Galactic Archaeology studies, with unprecedented detail, dimensionality, and scope.

  • 10.
    Da Costa, G. S.
    et al.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia.
    Bessell, M. S.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia.
    Mackey, A. D.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia;ARC Ctr Excellence Astrophys Three Dimens ASTRO 3, Canberra, ACT, Australia.
    Nordlander, T.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia;ARC Ctr Excellence Astrophys Three Dimens ASTRO 3, Canberra, ACT, Australia.
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia;ARC Ctr Excellence Astrophys Three Dimens ASTRO 3, Canberra, ACT, Australia.
    Casey, A. R.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia;Monash Univ, Sch Phys & Astron, Wellington Rd, Clayton, Vic 3800, Australia;Monash Univ, Fac Informat Technol, Wellington Rd, Clayton, Vic 3800, Australia.
    Frebel, A.
    MIT, Dept Phys, Cambridge, MA 02139 USA;MIT, Kavli Inst Astrophys & Space Res, Cambridge, MA 02139 USA.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-D69117 Heidelberg, Germany.
    Marino, A. F.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia;Univ Padua, Dipartimento Fis & Astron Galileo Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy;Ctr Ateneo & Attivita Spaziali Giuseppe Colombo C, Via Venezia 15, I-35131 Padua, Italy.
    Murphy, S. J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia;Univ New South Wales, Sch Sci, Canberra, ACT 2600, Australia.
    Norris, J. E.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia.
    Schmidt, B. P.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia.
    Yong, D.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia;ARC Ctr Excellence Astrophys Three Dimens ASTRO 3, Canberra, ACT, Australia.
    The SkyMapper DR1.1 search for extremely metal-poor stars2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 489, no 4, p. 5900-5918Article in journal (Refereed)
    Abstract [en]

    We present and discuss the results of a search for extremely metal-poor stars based on photometry from data release DR1.1 of the SkyMapper imaging survey of the southern sky. In particular, we outline our photometric selection procedures and describe the low-resolution (R approximate to 3000) spectroscopic follow-up observations that are used to provide estimates of effective temperature, surface gravity, and metallicity ([Fe/H]) for the candidates. The selection process is very efficient: of the 2618 candidates with low-resolution spectra that have photometric metallicity estimates less than or equal to -2.0, 41 per cent have [Fe/H] <= -2.75 and only approximately seven per cent have [Fe/H] > -2.0 dex. The most metal-poor candidate in the sample has [Fe/H] < -4.75 and is notably carbon rich. Except at the lowest metallicities ([Fe/H] < -4), the stars observed spectroscopically are dominated by a 'carbon-normal' population with [C/Fe](1D, LTE) <= +1 dex. Consideration of the A(C)(1D, LTE) versus [Fe/H](1D, LTE) diagram suggests that the current selection process is strongly biased against stars with A(C)(1D, LTE) > 7.3 (predominantly CEMP-s) while any bias against stars with A(C)(1D, LTE) < 7.3 and [C/Fe](1D, LTE) > +1 (predominantly CEMP-no) is not readily quantifiable given the uncertainty in the SkyMapper v-band DR1.1 photometry. We find that the metallicity distribution function of the observed sample has a power-law slope of Delta(Log N)/Delta[Fe/H] = 1.5 +/- 0.1 dex per dex for -4.0 <= [Fe/H] <= -2.75, but appears to drop abruptly at [Fe/H] approximate to -4.2, in line with previous studies.

  • 11. de Jong, Roelof S.
    et al.
    Barden, Sam
    Bellido-Tirado, Olga
    Brynnel, Joar
    Chiappini, Cristina
    Depagne, Eric
    Haynes, Roger
    Johl, Diane
    Phillips, Daniel P.
    Schnurr, Olivier
    Schwope, Axel
    Walcher, Jakob
    Bauer, Svend-Marian
    Cescutti, Gabriele
    Cioni, Maria-Rosa
    Dionies, Frank
    Enke, Harry
    Haynes, Dionne
    Kelz, Andreas
    Kitaura, Francisco S.
    Lamer, Georg
    Minchev, Ivan
    Mueler, Volker
    Nuza, Sebastian E.
    Olaya, Jean-Christophe
    Piffl, Tilman
    Popow, Emil
    Saviauk, Allar
    Steinmetz, Matthias
    Ural, Ugur
    Valentini, Monica
    Winkler, Roland
    Wisotzki, Lutz
    Ansorge, Wolfgang R.
    Banerji, Manda
    Solares, Eduardo Gonzalez
    Irwin, Mike
    Kennicutt, Robert C., Jr.
    King, David
    McMahon, Richard
    Koposov, Sergey
    Parry, Ian R.
    Sun, Xiaowei
    Walton, Nicholas A.
    Finger, Gert
    Iwert, Olaf
    Krumpe, Mirko
    Lizon, Jean-Louis
    Mainieri, Vincenzo
    Amans, Jean-Philippe
    Bonifacio, Piercarlo
    Cohen, Mathieu
    Francois, Patrick
    Jagourel, Pascal
    Mignot, Shan B.
    Royer, Frederic
    Sartoretti, Paola
    Bender, Ralf
    Hess, Hans-Joachim
    Lang-Bardl, Florian
    Muschielok, Bernard
    Schlichter, Jorg
    Bohringer, Hans
    Boller, Thomas
    Bongiorno, Angela
    Brusa, Marcella
    Dwelly, Tom
    Merloni, Andrea
    Nandra, Kirpal
    Salvato, Mara
    Pragt, Johannes H.
    Navarro, Ramon
    Gerlofsma, Gerrit
    Roelfsema, Ronald
    Dalton, Gavin B.
    Middleton, Kevin F.
    Tosh, Ian A.
    Boeche, Corrado
    Caffau, Elisabetta
    Chistlieb, Norbert
    Grebel, Eva K.
    Hansen, Camilla J.
    Koch, Andreas
    Ludwig, Hans-G.
    Mandel, Holger
    Quirrenbach, Andreas
    Sbordone, Luca
    Seifert, Walter
    Thimm, Guido
    Helmi, Amina
    Trager, Scott C.
    Bensby, Thomas
    Feltzing, Sofia
    Ruchti, Gregory
    Edvardsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Korn, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Boland, Wilfried
    Colless, Matthew
    Frost, Gabriella
    Gilbert, James
    Gillingham, Peter
    Lawrence, Jon
    Legg, Neville
    Saunders, Will
    Sheinis, Andrew
    Driver, Simon
    Robotham, Aaron
    Bacon, Roland
    Caillier, Patrick
    Kosmalski, Johan
    Laurent, Florence
    Richard, Johan
    4MOST-4-metre Multi-Object Spectroscopic Telescope2014In: GROUND-BASED AND AIRBORNE INSTRUMENTATION FOR ASTRONOMY V, 2014, Vol. 9147Conference paper (Refereed)
    Abstract [en]

    4MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory (ESO). Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. 4MOST will in particular provide the spectroscopic complements to the large area surveys coming from space missions like Gaia, eROSITA, Euclid, and PLATO and from ground-based facilities like VISTA, VST, DES, LSST and SKA. The 4MOST baseline concept features a 2.5 degree diameter field-of-view with similar to 2400 fibres in the focal surface that are configured by a fibre positioner based on the tilting spine principle. The fibres feed two types of spectrographs; similar to 1600 fibres go to two spectrographs with resolution R> 5000 (lambda similar to 390-930 nm) and similar to 800 fibres to a spectrograph with R> 18,000 (lambda similar to 392-437 nm & 515-572 nm & 605-675 nm). Both types of spectrographs are fixed-configuration, three-channel spectrographs. 4MOST will have an unique operations concept in which 5 year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure, resulting in more than 25 million spectra of targets spread over a large fraction of the southern sky. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing concept. 4MOST has been accepted for implementation by ESO with operations expected to start by the end of 2020. This paper provides a top-level overview of the 4MOST facility, while other papers in these proceedings provide more detailed descriptions of the instrument concept[1], the instrument requirements development[2], the systems engineering implementation[3], the instrument model[4], the fibre positioner concepts[5], the fibre feed[6], and the spectrographs[7].

  • 12. De Silva, G. M.
    et al.
    Freeman, K. C.
    Bland-Hawthorn, J.
    Martell, S.
    de Boer, E. Wylie
    Asplund, M.
    Keller, S.
    Sharma, S.
    Zucker, D. B.
    Zwitter, T.
    Anguiano, B.
    Bacigalupo, C.
    Bayliss, D.
    Beavis, M. A.
    Bergemann, M.
    Campbell, S.
    Cannon, R.
    Carollo, D.
    Casagrande, L.
    Casey, A. R.
    Da Costa, G.
    D'Orazi, V.
    Dotter, A.
    Duong, L.
    Heger, A.
    Ireland, M. J.
    Kafle, P. R.
    Kos, J.
    Lattanzio, J.
    Lewis, G. F.
    Lin, J.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Munari, U.
    Nataf, D. M.
    O'Toole, S.
    Parker, Q.
    Reid, W.
    Schlesinger, K. J.
    Sheinis, A.
    Simpson, J. D.
    Stello, D.
    Ting, Y. -S
    Traven, G.
    Watson, F.
    Wittenmyer, R.
    Yong, D.
    Zerjal, M.
    The GALAH survey: scientific motivation2015In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 449, no 3, p. 2604-2617Article in journal (Refereed)
    Abstract [en]

    The Galactic Archaeology with HERMES (GALAH) survey is a large high-resolution spectroscopic survey using the newly commissioned High Efficiency and Resolution Multi-Element Spectrograph (HERMES) on the Anglo-Australian Telescope. The HERMES spectrograph provides high-resolution (R similar to 28 000) spectra in four passbands for 392 stars simultaneously over a 2 deg field of view. The goal of the survey is to unravel the formation and evolutionary history of the Milky Way, using fossil remnants of ancient star formation events which have been disrupted and are now dispersed throughout the Galaxy. Chemical tagging seeks to identify such dispersed remnants solely from their common and unique chemical signatures; these groups are unidentifiable from their spatial, photometric or kinematic properties. To carry out chemical tagging, the GALAH survey will acquire spectra for a million stars down to V similar to 14. The HERMES spectra of FGK stars contain absorption lines from 29 elements including light proton-capture elements, alpha-elements, odd-Z elements, iron-peak elements and n-capture elements from the light and heavy s-process and the r-process. This paper describes the motivation and planned execution of the GALAH survey, and presents some results on the first-light performance of HERMES.

  • 13. Den Hartog, E. A.
    et al.
    Ruffoni, M. P.
    Lawler, J. E.
    Pickering, J. C.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Brewer, N. R.
    Fe I oscillator strengths for transitions from high-lying even-parity levels2014In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 215, no 2, p. 23-Article in journal (Refereed)
    Abstract [en]

    New radiative lifetimes, measured to +or-5% accuracy, are reported for 31 even-parity levels of Fe I ranging from 45061 cm -1 to 56842 cm -1. These lifetimes have been measured using single-step and two-step time-resolved laser-induced fluorescence on a slow atomic beam of iron atoms. Branching fractions have been attempted for all of these levels, and completed for 20 levels. This set of levels represents an extension of the collaborative work reported in Ruffoni et al. The radiative lifetimes combined with the branching fractions yields new oscillator strengths for 203 lines of Fe I. Utilizing a 1D-LTE model of the solar photosphere, spectral syntheses for a subset of these lines which are unblended in the solar spectrum yields a mean iron abundance of langlog[epsilon(Fe)]rang = 7.45 +or- 0.06.

  • 14.
    Duong, L.
    et al.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Freeman, K. C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Casagrande, L.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Buder, S.
    Max Planck Inst Astron, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Heidelberg, Germany.
    Ness, M.
    Max Planck Inst Astron, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Bland-Hawthorn, J.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    De Silva, G. M.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia;Australian Astron Observ, N Ryde, NSW 1670, Australia.
    D'Orazi, V.
    INAF, Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy.
    Kos, J.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Lewis, G. F.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Lin, J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Martell, S. L.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Schlesinger, K.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Sharma, S.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Simpson, J. D.
    Australian Astron Observ, N Ryde, NSW 1670, Australia.
    Zucker, D. B.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.
    Zwitter, T.
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Anguiano, B.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia;Univ Virginia, Dept Astron, POB 400325, Charlottesville, VA 22904 USA.
    Da Costa, G. S.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Hyde, E.
    Western Sydney Univ, Locked Bag 1797, Penrith, NSW 1797, Australia.
    Horner, J.
    Univ Southern Queensland, Toowoomba, Qld 4350, Australia.
    Kafle, P. R.
    Univ Western Australia, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia.
    Nataf, D. M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia;Johns Hopkins Univ, Ctr Astrophys Sci, Baltimore, MD 21218 USA;Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    Reid, W.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia;Western Sydney Univ, Locked Bag 1797, Penrith, NSW 2751, Australia;Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, DK-8000 Aarhus C, Denmark.
    Stello, D.
    Univ Sydney, Sch Phys A28, Sydney Inst Astron, Sydney, NSW 2006, Australia;Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia;Inst Adv Study, Olden Lane, Princeton, NJ 08540 USA.
    Ting, Y. -S
    Wyse, R. F. G.
    Johns Hopkins Univ, Ctr Astrophys Sci, Baltimore, MD 21218 USA;Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    The GALAH survey: properties of the Galactic disc(s) in the solar neighbourhood2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 476, no 4, p. 5216-5232Article in journal (Refereed)
    Abstract [en]

    Using data from the GALAH pilot survey, we determine properties of the Galactic thin and thick discs near the solar neighbourhood. The data cover a small range of Galactocentric radius (7.9 less than or similar to R-GC less than or similar to 9.5 kpc), but extend up to 4 kpc in height from the Galactic plane, and several kpc in the direction of Galactic anti-rotation (at longitude 260 degrees <= l <= 280 degrees). This allows us to reliably measure the vertical density and abundance profiles of the chemically and kinematically defined 'thick' and 'thin' discs of the Galaxy. The thin disc (low-alpha population) exhibits a steep negative vertical metallicity gradient, at d[M/H]/dz = -0.18 +/- 0.01 dex kpc(-1), which is broadly consistent with previous studies. In contrast, its vertical alpha-abundance profile is almost flat, with a gradient of d[alpha/M]/dz = 0.008 +/- 0.002 dex kpc(-1). The steep vertical metallicity gradient of the low-a population is in agreement with models where radial migration has a major role in the evolution of the thin disc. The thick disc (high-alpha population) has a weaker vertical metallicity gradient d[M/H]/dz = -0.058 +/- 0.003 dex kpc(-1). The aabundance of the thick disc is nearly constant with height, d[alpha/M]/dz = 0.007 +/- 0.002 dex kpc(-1). The negative gradient in metallicity and the small gradient in [alpha/M] indicate that the high-alpha population experienced a settling phase, but also formed prior to the onset of major Type I alpha supernova enrichment. We explore the implications of the distinct alpha-enrichments and narrow [alpha/M] range of the sub-populations in the context of thick disc formation.

  • 15.
    Feuillet, Diane K.
    et al.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Frankel, Neige
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Frinchaboy, Peter M.
    Texas Christian Univ, Dept Phys & Astron, Ft Worth, TX 76129 USA.
    Garcia-Hernandez, D. A.
    IAC, E-38205 Tenerife, Spain;ULL, Dept Astrofis, E-38205 Tenerife, Spain.
    Lane, Richard R.
    Pontificia Univ Catolica Chile, Inst Astrofis, Av Vicuna Mackenna 4860, Santiago 7820436, Chile;Millennium Inst Astrophys, Av Vicuna Mackenna 4860, Santiago 7820436, Chile.
    Nitschelm, Christian
    Univ Antofagasta, Ctr Astron CITEVA, Ave Angamos 601, Antofagasta 1270300, Chile.
    Roman-Lopes, Alexandre
    Univ La Serena, Fac Ciencias, Dept Fis, Cisterns 1200, La Serena, Chile.
    Spatial variations in the Milky Way disc metallicity-age relation2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 489, no 2, p. 1742-1752Article in journal (Refereed)
    Abstract [en]

    Stellar ages are a crucial component to studying the evolution of the Milky Way. Using Gaia DR2 distance estimates, it is now possible to estimate stellar ages for a larger volume of evolved stars through isochrone matching. This work presents [M/H]-age and [alpha/M]-age relations derived for different spatial locations in the Milky Way disc. These relations are derived by hierarchically modelling the star formation history of stars within a given chemical abundance bin. For the first time, we directly observe that significant variation is apparent in the [M/H]-age relation as a function of both Galactocentric radius and distance from the disc midplane. The [M/H]-age relations support claims that radial migration has a significant effect in the plane of the disc. Using the [M/H] bin with the youngest mean age at each radial zone in the plane of the disc, the present-day metallicity gradient is measured to be -0.059 +/- 0.010 dex kpc(-1), in agreement with Cepheids and young field stars. We find a vertically flared distribution of young stars in the outer disc, confirming predictions of models and previous observations. The mean age of the [M/H]-[alpha/M] distribution of the solar neighbourhood suggests that the high-[M/H] stars are not an evolutionary extension of the low-alpha sequence. Our observational results are important constraints to Galactic simulations and models of chemical evolution.

  • 16.
    Gao, Xudong
    et al.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.;Heidelberg Univ, Int Max Planck Res Sch Astron & Cosm Phys, Heidelberg, Germany..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Amarsi, Anish M.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Buder, Sven
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.;Heidelberg Univ, Int Max Planck Res Sch Astron & Cosm Phys, Heidelberg, Germany..
    Dotter, Aaron
    Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA..
    Nordlander, Thomas
    Australian Natl Univ, Mt Stromlo Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT 2611, Australia..
    Asplund, Martin
    Australian Natl Univ, Mt Stromlo Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT 2611, Australia..
    Bland-Hawthorn, Joss
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT 2611, Australia.;Univ Sydney, Sch Phys, Sydney Inst Astron SIfA, A28, Sydney, NSW 2006, Australia.;Univ Calif Berkeley, Miller Inst, Berkeley, CA 94720 USA..
    De Silva, Gayandhi M.
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT 2611, Australia.;Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia..
    D'Orazi, Valentina
    Osserv Astron Padova, Ist Nazl Astrofis, Vicolo Osservatorio 5, I-35122 Padua, Italy..
    Freeman, Ken C.
    Australian Natl Univ, Mt Stromlo Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia..
    Kos, Janez
    Univ Sydney, Sch Phys, Sydney Inst Astron SIfA, A28, Sydney, NSW 2006, Australia..
    Lewis, Geraint F.
    Univ Sydney, Sch Phys, Sydney Inst Astron SIfA, A28, Sydney, NSW 2006, Australia..
    Lin, Jane
    Australian Natl Univ, Mt Stromlo Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT 2611, Australia..
    Martell, Sarah L.
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT 2611, Australia.;Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia..
    Schlesinger, Katharine J.
    Australian Natl Univ, Mt Stromlo Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia..
    Sharma, Sanjib
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT 2611, Australia.;Univ Sydney, Sch Phys, Sydney Inst Astron SIfA, A28, Sydney, NSW 2006, Australia..
    Simpson, Jeffrey D.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia..
    Zucker, Daniel B.
    Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia.;Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia..
    Zwitter, Tomaz
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia..
    Da Costa, Gary
    Australian Natl Univ, Mt Stromlo Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia..
    Anguiano, Borja
    Univ Virginia, Dept Astron, POB 400325, Charlottesville, VA 22904 USA..
    Horner, Jonathan
    Univ Southern Queensland, Toowoomba, Qld 4350, Australia..
    Hyde, Elaina A.
    Western Sydney Univ, Locked Bag 1797, Penrith, NSW 1797, Australia..
    Kafle, Prajwal R.
    Univ Western Australia, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia..
    Nataf, David M.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA..
    Reid, Warren
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.;Western Sydney Univ, Locked Bag 1797, Penrith, NSW 1797, Australia..
    Stello, Dennis
    Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT 2611, Australia.;Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.;Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, DK-8000 Aarhus C, Denmark..
    Ting, Yuan-Sen
    Inst Adv Study, Princeton, NJ 08540 USA.;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA.;Observ Carnegie Inst Washington, 813 Santa Barbara St, Pasadena, CA 91101 USA..
    The GALAH survey: verifying abundance trends in the open cluster M67 using non-LTE modelling2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 481, no 2, p. 2666-2684Article in journal (Refereed)
    Abstract [en]

    Open cluster members are coeval and share the same initial bulk chemical composition. Consequently, differences in surface abundances between members of a cluster that are at different evolutionary stages can be used to study the effects of mixing and internal chemical processing. We carry out an abundance analysis of seven elements (Li, O, Na, Mg, Al, Si, and Fe) in 66 stars belonging to the open cluster m67, based on high resolution GALAH spectra, 1D MARCS model atmospheres, and non-local thermodynamic equilibrium (non-LTE) radiative transfer. From the non-LTE analysis, we find a typical star-to-star scatter in the abundance ratios of around O.05 dex. We find trends in the abundance ratios with effective temperature, indicating systematic differences in the surface abundances between turn-off and giant stars; these trends are more pronounced when LTE is assumed. However, trends with effective temperature remain significant for Al and Si also in non-LTE. Finally, we compare the derived abundances with prediction from stellar evolution models including effects of atomic diffusion. We find overall good agreement for the abundance patterns of dwarfs and sub-giant stars, but the abundances of cool giants are lower relative to less evolved stars than predicted by the diffusion models, in particular for Mg.

  • 17.
    Gavel, Alvin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Gruyters, Pieter
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Korn, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Nordlander, Thomas
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia;Arc Ctr Excellence All Sky Astrophys 3 Dimens AST, Sydney, NSW, Australia.
    The LUMBA UVES stellar parameter pipeline2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 629, article id A74Article in journal (Refereed)
    Abstract [en]

    Context. The Gaia-ESO Survey has taken high-quality spectra of a subset of 100 000 stars observed with the Gaia spacecraft. The goal for this subset is to derive chemical abundances for these stars that will complement the astrometric data collected by Gaia. Deriving the chemical abundances requires that the stellar parameters be determined. Aims. We present a pipeline for deriving stellar parameters from spectra observed with the FLAMES-UVES spectrograph in its standard fibre-fed mode centred on 580 nm, as used in the Gaia-ESO Survey. We quantify the performance of the pipeline in terms of systematic offsets and scatter. In doing so, we present a general method for benchmarking stellar parameter determination pipelines. Methods. Assuming a general model of the errors in stellar parameter pipelines, together with a sample of spectra of stars whose stellar parameters are known from fundamental measurements and relations, we use a Markov chain Monte Carlo method to quantitatively test the pipeline. Results. We find that the pipeline provides parameter estimates with systematic errors on effective temperature below 100 K, on surface gravity below 0.1 dex, and on metallicity below 0.05 dex for the main spectral types of star observed in the Gaia-ESO Survey and tested here. The performance on red giants is somewhat lower. Conclusions. The pipeline performs well enough to fulfil its intended purpose within the Gaia-ESO Survey. It is also general enough that it can be put to use on spectra from other surveys or other spectrographs similar to FLAMES-UVES.

  • 18.
    Gruyters, Pieter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Lund Observ, Box 43, S-22100 Lund, Sweden..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Richard, Olivier
    Univ Montpellier, CNRS, LUPM, CC072,Pl E Bataillon, F-34095 Montpellier, France..
    Grundahl, Frank
    Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Asplund, Martin
    Australian Natl Univ, Mt Stromlo Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia..
    Casagrande, Luca
    Australian Natl Univ, Mt Stromlo Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia..
    Charbonnel, Corinne
    Univ Geneva, Dept Astron, Chemin Maillettes 51, CH-1290 Versoix, Switzerland.;Univ Toulouse, CNRS UMR 5277, IRAP, 14 Ave E Belin, F-31400 Toulouse, France..
    Milone, Antonino
    Australian Natl Univ, Mt Stromlo Observ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia..
    Primas, Francesca
    European So Observ, D-85748 Garching, Germany..
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Atomic diffusion and mixing in old stars VI. The lithium content of M302016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 589, article id A61Article in journal (Refereed)
    Abstract [en]

    Context. The prediction of the Planck-constrained primordial lithium abundance in the Universe is in discordance with the observed Li abundances in warm Population II dwarf and subgiant stars. Among the physically best motivated ideas, it has been suggested that this discrepancy can be alleviated if the stars observed today had undergone photospheric depletion of lithium.

    Aims. The cause of this depletion is investigated by accurately tracing the behaviour of the lithium abundances as a function of effective temperature. Globular clusters are ideal laboratories for such an abundance analysis as the relative stellar parameters of their stars can be precisely determined.

    Methods. We performed a homogeneous chemical abundance analysis of 144 stars in the metal-poor globular cluster M30, ranging from the cluster turnoff point to the tip of the red giant branch. Non-local thermal equilibrium (NLTE) abundances for Li, Ca, and Fe were derived where possible by fitting spectra obtained with VLT/FLAMES-GIRAFFE using the quantitative-spectroscopy package SME. Stellar parameters were derived by matching isochrones to the observed V vs. V I colour-magnitude diagram. Independent effective temperatures were obtained from automated profile fitting of the Balmer lines and by applying colour-T-eff calibrations to the broadband photometry.

    Results. Li abundances of the turno ff and early subgiant stars form a thin plateau that is broken off abruptly in the middle of the SGB as a result of the onset of Li dilution caused by the first dredge-up. Abundance trends with effective temperature for Fe and Ca are observed and compared to predictions from stellar structure models including atomic diffusion and ad hoc additional mixing below the surface convection zone. The comparison shows that the stars in M30 are affected by atomic diffusion and additional mixing, but we were unable to determine the efficiency of the additional mixing precisely. This is the fourth globular cluster (after NGC6397, NGC6752, and M4) in which atomic diffusion signatures are detected. After applying a conservative correction (T6.0 model) for atomic diffusion, we find an initial Li abundance of A(Li) = 2.48 +/- 0.10 for the globular cluster M30. We also detected a Li-rich SGB star with a Li abundance of A(Li) = 2.39. The finding makes Li-rich mass transfer a likely scenario for this star and rules out models in which its Li enhancement is created during the RGB bump phase.

  • 19.
    Guiglion, G.
    et al.
    Univ Cote Azur, Lab Lagrange, CNRS, Observ Cote Azur, F-06304 Nice 4, France..
    Recio-Blanco, A.
    Univ Cote Azur, Lab Lagrange, CNRS, Observ Cote Azur, F-06304 Nice 4, France..
    de Laverny, P.
    Univ Cote Azur, Lab Lagrange, CNRS, Observ Cote Azur, F-06304 Nice 4, France..
    Kordopatis, G.
    Leibniz Inst Astrophys Potsdam AIP, D-14482 Potsdam, Germany..
    Hill, V.
    Univ Cote Azur, Lab Lagrange, CNRS, Observ Cote Azur, F-06304 Nice 4, France..
    Mikolaitis, S.
    Univ Cote Azur, Lab Lagrange, CNRS, Observ Cote Azur, F-06304 Nice 4, France..
    Minchev, I.
    Leibniz Inst Astrophys Potsdam AIP, D-14482 Potsdam, Germany..
    Chiappini, C.
    Leibniz Inst Astrophys Potsdam AIP, D-14482 Potsdam, Germany..
    Wyse, R. F. G.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA..
    Gilmore, G.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Randich, S.
    Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy..
    Feltzing, S.
    Lund Observ, Dept Astron & Theoret Phys, S-22100 Lund, Sweden..
    Bensby, T.
    Lund Observ, Dept Astron & Theoret Phys, S-22100 Lund, Sweden..
    Flaccomio, E.
    Osserv Astron Palermo, INAF, I-90134 Palermo, Italy..
    Koposov, S. E.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England.;Moscow MV Lomonosov State Univ, Sternberg Astron Inst, Moscow 119992, Russia..
    Pancino, E.
    Osservatorio Astron Bologna, INAF, I-40127 Bologna, Italy.;ASI Sci Data Ctr, I-00133 Rome, Italy..
    Bayo, A.
    Univ Valparaiso, Inst Fis & Astron, Valparaiso 2360102, Chile..
    Costado, M. T.
    CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain..
    Franciosini, E.
    Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy..
    Hourihane, A.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Jofre, P.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Lardo, C.
    Liverpool John Moores Univ, Astrophys Res Inst, Liverpool L3 5RF, Merseyside, England..
    Lewis, J.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Magrini, L.
    Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy..
    Morbidelli, L.
    Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy..
    Sacco, G. G.
    Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy..
    Ruchti, G.
    Lund Observ, Dept Astron & Theoret Phys, S-22100 Lund, Sweden..
    Worley, C. C.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Zaggia, S.
    Padova Observ, INAF, I-35122 Padua, Italy..
    The Gaia-ESO Survey: New constraints on the Galactic disc velocity dispersion and its chemical dependencies2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, article id A91Article in journal (Refereed)
    Abstract [en]

    Context. Understanding the history and the evolution of the Milky Way is one of the main goals of modern astrophysics. In particular, the formation of the Galactic disc is a key problem of Galactic archaeology. Aims. We study the velocity dispersion behaviour of Galactic disc stars as a function of the [Mg/Fe] ratio, which for small metallicity bins can be used as a proxy of relative age. This key relation is essential to constrain the formation mechanisms of the disc stellar populations as well as the cooling and settling processes. Methods. We used the recommended parameters and chemical abundances of 7800 FGK Milky Way field stars from the second internal data release of the Gaia-ESO spectroscopic Survey. These stars were observed with the GIRAFFE spectrograph (HR10 and HR21 setups), and cover a large spatial volume in the intervals 6 < R < 10 kpc and vertical bar Z vertical bar < 2 kpc. Based on a chemical criterion, we separated the thin- from the thick-disc sequence in the [Mg/Fe] vs. [Fe/H] plane. Results. From analysing the Galactocentric velocity of the stars for the thin disc, we find a weak positive correlation between 170 and [Fe/H] that is due to a slowly rotating [Fe/H]-poor tail. For the thick disc stars, a strong correlation with [Fe/H] and [Mg/Fe] is established. In addition, we have detected an inversion of the velocity dispersion trends with [Mg/Fe] for thick-disc stars with [Fe/H] < -0.10 dex and [Mg/Fe] > +0.20 dex for the radial component. First, the velocity dispersion increases with [Mg/Fe] at all [Fe/H] ratios for the thin-disc stars, and then it decreases for the thick-disc population at the highest [Mg/Fe] abundances Similar trends are observed for several bins of [Mg/Fe] within the errors for the azimuthal velocity dispersion, while a continuous increase with [Mg/Fe] is observed for the vertical velocity dispersion. The velocity dispersion decrease agrees with previous measurements of the RAVE survey, although it is observed here for a greater metallicity interval and a larger spatial volume. Conclusions. Thanks to the Gaia-ESO Survey data, we confirm the existence of [Mg/Fe]-rich thick-disc stars with cool kinematics in the generally turbulent context of the primitive Galactic disc. This is discussed in the framework of the different disc formation and evolution scenarios.

  • 20.
    Hansen, C. J.
    et al.
    Heidelberg Univ, Zentrum Astron, D-69117 Heidelberg, Germany.;Univ Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, DK-2100 Copenhagen, Denmark..
    Ludwig, H. -G
    Seifert, W.
    Heidelberg Univ, Zentrum Astron, D-69117 Heidelberg, Germany..
    Koch, A.
    Heidelberg Univ, Zentrum Astron, D-69117 Heidelberg, Germany..
    Xu, W.
    Opt Syst Engn, D-74937 Spechbach, Germany..
    Caffau, E.
    Univ Paris Diderot, CNRS, Observ Paris, GEPI, F-92190 Meudon, France..
    Christlieb, N.
    Heidelberg Univ, Zentrum Astron, D-69117 Heidelberg, Germany..
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Sbordone, L.
    Millennium Inst Astrophys, Santiago, Chile.;Pontificia Univ Catolica Chilem, Santiago, Chile..
    Ruchti, G.
    Lund Observ, Dept Astron & Theoret Phys, SE-22100 Lund, Sweden..
    Feltzing, S.
    Lund Observ, Dept Astron & Theoret Phys, SE-22100 Lund, Sweden..
    de Jong, R. S.
    Leibniz Inst Astrophys Potsdam, D-14482 Potsdam, Germany..
    Barden, S.
    Leibniz Inst Astrophys Potsdam, D-14482 Potsdam, Germany..
    Schnurr, O.
    Leibniz Inst Astrophys Potsdam, D-14482 Potsdam, Germany..
    Stellar science from a blue wavelength range2015In: Astronomical Notes - Astronomische Nachrichten, ISSN 0004-6337, E-ISSN 1521-3994, Vol. 336, no 7, p. 665-676Article in journal (Refereed)
    Abstract [en]

    From stellar spectra, a variety of physical properties of stars can be derived. In particular, the chemical composition of stellar atmospheres can be inferred from absorption line analyses. These provide key information on large scales, such as the formation of our Galaxy, down to the small-scale nucleosynthesis processes that take place in stars and supernovae. By extending the observed wavelength range toward bluer wavelengths, we optimize such studies to also include critical absorption lines in metal-poor stars, and allow for studies of heavy elements (Z = 38) whose formation processes remain poorly constrained. In this context, spectrographs optimized for observing blue wavelength ranges are essential, since many absorption lines at redder wavelengths are too weak to be detected in metal-poor stars. This means that some elements cannot be studied in the visual-redder regions, and important scientific tracers and science cases are lost. The present era of large public surveys will target millions of stars. It is therefore important that the next generation of spectrographs are designed such that they cover a wide wavelength range and can observe a large number of stars simultaneously. Only then, we can gain the full information from stellar spectra, from both metal-poor to metal-rich ones, that will allow us to understand the aforementioned formation scenarios in greater detail. Here we describe the requirements driving the design of the forthcoming survey instrument 4MOST, a multi-object spectrograph commissioned for the ESO VISTA 4 m-telescope. While 4MOST is also intended for studies of active galactic nuclei, baryonic acoustic oscillations, weak lensing, cosmological constants, supernovae and other transients, we focus here on high-density, wide-area survey of stars and the science that can be achieved with high-resolution stellar spectroscopy. Scientific and technical requirements that governed the design are described along with a thorough line blending analysis. For the high-resolution spectrograph, we find that a sampling of >= 2.5 (pixels per resolving element), spectral resolution of 18 000 or higher, and a wavelength range covering 393-436 nm, is the most well-balanced solution for the instrument. A spectrograph with these characteristics will enable accurate abundance analysis (+/- 0.1 dex) in the blue and allow us to confront the outlined scientific questions.

  • 21.
    Hayden, M. R.
    et al.
    Univ Nice Sophia Antipolis, Lab Lagrange UMR 7293, CNRS, Observ Cote Azur, BP 4229, F-06304 Nice 4, France..
    Recio-Blanco, A.
    Univ Nice Sophia Antipolis, Lab Lagrange UMR 7293, CNRS, Observ Cote Azur, BP 4229, F-06304 Nice 4, France..
    de Laverny, P.
    Univ Nice Sophia Antipolis, Lab Lagrange UMR 7293, CNRS, Observ Cote Azur, BP 4229, F-06304 Nice 4, France..
    Mikolaitis, S.
    Vilnius Univ, Inst Theoret Phys & Astron, Sauletekio Al 3, LT-10257 Vilnius, Lithuania..
    Guiglion, G.
    Univ Nice Sophia Antipolis, Lab Lagrange UMR 7293, CNRS, Observ Cote Azur, BP 4229, F-06304 Nice 4, France..
    Hill, V.
    Univ Nice Sophia Antipolis, Lab Lagrange UMR 7293, CNRS, Observ Cote Azur, BP 4229, F-06304 Nice 4, France..
    Gilmore, G.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Randich, S.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Bayo, A.
    Univ Valparaso, Inst Fis & Astron, Fac Ciencias, Ave Gran Bretana 1111, Valparaiso 5030, Chile.;Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Bensby, T.
    Lund Observ, Dept Astron & Theoret Phys, Box 43, S-22100 Lund, Sweden..
    Bergemann, M.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Bragaglia, A.
    INAF Osservatorio Astron Bologna, Via Ranzani 1, I-40127 Bologna, Italy..
    Casey, A.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Costado, M.
    CSIC, Inst Astrofis Andalucia, Apdo 3004, E-18080 Granada, Spain..
    Feltzing, S.
    Lund Observ, Dept Astron & Theoret Phys, Box 43, S-22100 Lund, Sweden..
    Franciosini, E.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Hourihane, A.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Jofre, P.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Koposov, S.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Kordopatis, G.
    Leibniz Inst Astrophys Potsdam AIP, Sternwarte 16, D-14482 Potsdam, Germany..
    Lanzafame, A.
    Univ Catania, Dipartimento Fis & Astron, Sez Astrofis, Via S Sofia 78, I-95123 Catania, Italy.;INAF Osservatorio Astrofis Catania, Via S Sofia 78, I-95123 Catania, Italy..
    Lardo, C.
    Liverpool John Moores Univ, Astrophys Res Inst, 146 Brownlow Hill, Liverpool L3 5RF, Merseyside, England..
    Lewis, J.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy.
    Magrini, L.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Monaco, L.
    Univ Andres Bello, Dept Ciencias Fis, Republ 220, Santiago, Chile..
    Morbidelli, L.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Pancino, E.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Sacco, G.
    INAF Osservatorio Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Stonkute, E.
    Vilnius Univ, Inst Theoret Phys & Astron, Sauletekio Al 3, LT-10257 Vilnius, Lithuania.;Lund Observ, Dept Astron & Theoret Phys, Box 43, S-22100 Lund, Sweden..
    Worley, C. C.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Zwitter, T.
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia..
    The Gaia-ESO Survey: Churning through the Milky Way2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 609, article id A79Article in journal (Refereed)
    Abstract [en]

    Context: There have been conflicting results with respect to the extent that radial migration has played in the evolution of the Galaxy. Additionally, observations of the solar neighborhood have shown evidence of a merger in the past history of the Milky Way that drives enhanced radial migration.

    Aims: We attempt to determine the relative fraction of stars that have undergone significant radial migration by studying the orbital properties of metal-rich ([Fe/H] > 0.1) stars within 2 kpc of the Sun. We also aim to investigate the kinematic properties, such as velocity dispersion and orbital parameters, of stellar populations near the Sun as a function of [Mg/Fe] and [Fe/H], which could show evidence of a major merger in the past history of the Milky Way.

    Methods: We used a sample of more than 3000 stars selected from the fourth internal data release of the Gaia-ESO Survey. We used the stellar parameters from the Gaia-ESO Survey along with proper motions from PPMXL to determine distances, kinematics, and orbital properties for these stars to analyze the chemodynamic properties of stellar populations near the Sun.

    Results: Analyzing the kinematics of the most metal-rich stars ([Fe/H] > 0 : 1), we find that more than half have small eccentricities (e < 0 : 2) or are on nearly circular orbits. Slightly more than 20% of the metal-rich stars have perigalacticons R-p > 7 kpc. We find that the highest [Mg/ Fe], metal-poor populations have lower vertical and radial velocity dispersions compared to lower [Mg/Fe] populations of similar metallicity by similar to 10 km s(-1). The median eccentricity increases linearly with [Mg/Fe] across all metallicities, while the perigalacticon decreases with increasing [Mg/Fe] for all metallicities. Finally, the most [Mg/Fe]-rich stars are found to have significant asymmetric drift and rotate more than 40 km s(-1) slower than stars with lower [Mg/Fe] ratios.

    Conclusions: While our results cannot constrain how far stars have migrated, we propose that migration processes are likely to have played an important role in the evolution of the Milky Way, with metal-rich stars migrating from the inner disk toward to solar neighborhood and past mergers potentially driving enhanced migration of older stellar populations in the disk.

  • 22.
    Heiter, Ulrike
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Asplund, M.
    Barklem, Paul S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Bergemann, M.
    Magrini, L.
    Masseron, T.
    Mikolaitis, S.
    Pickering, J. C.
    Ruffoni, M. P.
    Atomic and molecular data for optical stellar spectroscopy2015In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 90, no 5, article id 054010Article in journal (Refereed)
    Abstract [en]

    High-precision spectroscopy of large stellar samples plays a crucial role for several topical issues in astrophysics. Examples include studying the chemical structure and evolution of the Milky Way Galaxy, tracing the origin of chemical elements, and characterizing planetary host stars. Data are accumulating from instruments that obtain high-quality spectra of stars in the ultraviolet, optical and infrared wavelength regions on a routine basis. These instruments are located at ground-based 2-10 m class telescopes around the world, in addition to the spectrographs with unique capabilities available at the Hubble Space Telescope. The interpretation of these spectra requires high-quality transition data for numerous species, in particular neutral and singly ionized atoms, and di-or triatomic molecules. We rely heavily on the continuous efforts of laboratory astrophysics groups that produce and improve the relevant experimental and theoretical atomic and molecular data. The compilation of the best available data is facilitated by databases and electronic infrastructures such as the NIST Atomic Spectra Database, the VALD database, or the Virtual Atomic and Molecular Data Centre. We illustrate the current status of atomic data for optical stellar spectra with the example of the Gaia-ESO Public Spectroscopic Survey. Data sources for 35 chemical elements were reviewed in an effort to construct a line list for a homogeneous abundance analysis of up to 10(5) stars.

  • 23. Howes, L. M.
    et al.
    Asplund, M.
    Casey, A. R.
    Keller, S. C.
    Yong, D.
    Gilmore, G.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Worley, C.
    Bessell, M. S.
    Casagrande, L.
    Marino, A. F.
    Nataf, D. M.
    Owen, C. I.
    Da Costa, G. S.
    Schmidt, B. P.
    Tisserand, P.
    Randich, S.
    Feltzing, S.
    Vallenari, A.
    Allende Prieto, C.
    Bensby, T.
    Flaccomio, E.
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Pancino, E.
    Recio-Blanco, A.
    Smiljanic, R.
    Bergemann, M.
    Costado, M. T.
    Damiani, F.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Hill, V.
    Hourihane, A.
    Jofre, P.
    Lardo, C.
    de laverny, P.
    Magrini, L.
    Maiorca, E.
    Masseron, T.
    Morbidelli, L.
    Sacco, G. G.
    Minniti, D.
    Zoccali, M.
    The Gaia-ESO Survey: the most metal-poor stars in the Galactic bulge2014In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 445, no 4, p. 4241-4246Article in journal (Refereed)
    Abstract [en]

    We present the first results of the EMBLA survey (Extremely Metal-poor BuLge stars with AAOmega), aimed at finding metal-poor stars in the Milky Way bulge, where the oldest stars should now preferentially reside. EMBLA utilizes SkyMapper photometry to pre-select metal-poor candidates, which are subsequently confirmed using AAOmega spectroscopy. We describe the discovery and analysis of four bulge giants with -2.72 <= [Fe/H] <= -2.48, the lowest metallicity bulge stars studied with high-resolution spectroscopy to date. Using FLAMES/UVES spectra through the Gaia-ESO Survey we have derived abundances of twelve elements. Given the uncertainties, we find a chemical similarity between these bulge stars and halo stars of the same metallicity, although the abundance scatter may be larger, with some of the stars showing unusual [alpha/Fe] ratios.

  • 24.
    Howes, L. M.
    et al.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia..
    Casey, A. R.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia..
    Keller, S. C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia..
    Yong, D.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia..
    Nataf, D. M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia..
    Poleski, R.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland.;Ohio State Univ, Dept Astron, Columbus, OH 43210 USA..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Kobayashi, C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia.;Univ Hertfordshire, Sch Phys Astron & Math, Ctr Astrophys Res, Hatfield AL10 9AB, Herts, England..
    Owen, C. I.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia..
    Ness, M.
    Max Planck Inst Astron, D-69117 Heidelberg, Germany..
    Bessell, M. S.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia..
    Da Costa, G. S.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia..
    Schmidt, B. P.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia..
    Tisserand, P.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2601, Australia.;Univ Paris 06, Univ Paris 04, F-75014 Paris, France.;CNRS, Inst Astrophys Paris, UMR 7095, F-75014 Paris, France..
    Udalski, A.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland..
    Szymanski, M. K.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland..
    Soszynski, I.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland..
    Pietrzynski, G.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland.;Univ Concepcion, Dept Astron, Concepcion, Chile..
    Ulaczyk, K.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland.;Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England..
    Wyrzykowski, L.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland..
    Pietrukowicz, P.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland..
    Skowron, J.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland..
    Kozlowski, S.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland..
    Mroz, P.
    Univ Warsaw Observ, PL-00473 Warsaw, Poland..
    Extremely metal-poor stars from the cosmic dawn in the bulge of the Milky Way2015In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 527, no 7579, p. 484-487Article in journal (Refereed)
    Abstract [en]

    The first stars are predicted to have formed within 200 million years after the Big Bang(1), initiating the cosmic dawn. A true first star has not yet been discovered, although stars(2-4) with tiny amounts of elements heavier than helium ('metals') have been found in the outer regions ('halo') of the Milky Way. The first stars and their immediate successors should, however, preferentially be found today in the central regions ('bulges') of galaxies, because they formed in the largest over-densities that grew gravitationally with time(5,6). The Milky Way bulge underwent a rapid chemical enrichment during the first 1-2 billion years(7), leading to a dearth of early, metal-poor stars(8,9). Here we report observations of extremely metal-poor stars in the Milky Way bulge, including one star with an iron abundance about 10,000 times lower than the solar value without noticeable carbon enhancement. We confirm that most of the metal-poor bulge stars are on tight orbits around the Galactic Centre, rather than being halo stars passing through the bulge, as expected for stars formed at redshifts greater than 15. Their chemical compositions are in general similar to typical halo stars of the same metallicity although intriguing differences exist, including lower abundances of carbon.

  • 25.
    Howes, Louise M.
    et al.
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia.;Lund Univ, Dept Astron & Theoret Phys, Lund Observ, Box 43, SE-22100 Lund, Sweden..
    Asplund, Martin
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia..
    Keller, Stefan C.
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia..
    Casey, Andrew R.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Yong, David
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Frebel, Anna
    MIT, Kavli Inst Astrophys & Space Res, 77 Massachusetts Ave, Cambridge, MA 02139 USA..
    Hays, Austin
    MIT, Kavli Inst Astrophys & Space Res, 77 Massachusetts Ave, Cambridge, MA 02139 USA..
    Alves-Brito, Alan
    Univ Fed Rio Grande do Sul, Inst Fis, BR-91501970 Porto Alegre, RS, Brazil..
    Bessell, Michael S.
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia..
    Casagrande, Luca
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia..
    Marino, Anna F.
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia..
    Nataf, David M.
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia..
    Owen, Christopher I.
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia..
    Da Costa, Gary S.
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia..
    Schmidt, Brian P.
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia..
    Tisserand, Patrick
    Mt Stromlo & Siding Spring Observ, Res Sch Astron & Astrophys, Cotter Rd, Weston, ACT 2611, Australia.;Univ Paris 06, Univ Paris 04, 98 Bis Bd Arago, F-75014 Paris, France.;CNRS, UMR 7095, Inst Astrophys Paris, 98 Bis Bd Arago, F-75014 Paris, France..
    The EMBLA survey - metal-poor stars in the Galactic bulge2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 460, no 1, p. 884-901Article in journal (Refereed)
    Abstract [en]

    Cosmological models predict the oldest stars in the Galaxy should be found closest to the centre of the potential well, in the bulge. The Extremely Metal-poor BuLge stars with AAOmega survey (EMBLA) successfully searched for these old, metal-poor stars by making use of the distinctive SkyMapper photometric filters to discover candidate metal-poor stars in the bulge. Their metal-poor nature was then confirmed using the AAOmega spectrograph on the Anglo-Australian Telescope. Here we present an abundance analysis of 10 bulge stars with -2.8 < [Fe/H] < -1.7 from MIKE/Magellan observations, in total determining the abundances of 22 elements. Combining these results with our previous high-resolution data taken as part of the Gaia-ESO Survey, we have started to put together a picture of the chemical and kinematic nature of the most metal-poor stars in the bulge. The currently available kinematic data are consistent with the stars belonging to the bulge, although more accurate measurements are needed to constrain the stars' orbits. The chemistry of these bulge stars deviates from that found in halo stars of the same metallicity. Two notable differences are the absence of carbon-enhanced metal-poor bulge stars, and the alpha element abundances exhibit a large intrinsic scatter and include stars which are underabundant in these typically enhanced elements.

  • 26.
    Jackson, R. J.
    et al.
    Keele Univ, Astrophys Grp, Keele ST5 5BG, Staffs, England..
    Jeffries, R. D.
    Keele Univ, Astrophys Grp, Keele ST5 5BG, Staffs, England..
    Lewis, J.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Koposov, S. E.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England.;Moscow MV Lomonosov State Univ, Sternberg Astron Inst, Moscow 119992, Russia..
    Sacco, G. G.
    Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy..
    Randich, S.
    Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy..
    Gilmore, G.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia..
    Binney, J.
    Rudolf Peierls Ctr Theoret Phys, Oxford OX1 3NP, England..
    Bonifacio, P.
    Univ Paris Diderot, CNRS, Observ Paris, GERI, F-92190 Meudon, France..
    Drew, J. E.
    Univ Hertfordshire, STRI, Ctr Astrophys Res, Hatfield AL10 9AB, Herts, England..
    Feltzing, S.
    Lund Observ, Dept Astron & Theoret Phys, S-22100 Lund, Sweden..
    Ferguson, A. M. N.
    Univ Edinburgh, Inst Astron, Edinburgh EH9 3HJ, Midlothian, Scotland..
    Micela, G.
    Osserv Astron Palermo, INAF, I-90134 Palermo, Italy..
    Neguerela, I.
    Univ Alicante, Dept Fis Ingn Sistemas & Teor Senal, E-03080 Alicante, Spain..
    Prusti, T.
    European Space Agcy, Estec, NL-2200 AG Noordwijk, Netherlands..
    Rix, H. -W
    Vallenari, A.
    INAF Padova Observ, I-35122 Padua, Italy..
    Alfaro, E. J.
    CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain..
    Prieto, C. Allende
    Inst Astrofis Canarias, Tenerife 38205, Spain.;Univ La Laguna, Dept Astrofis, E-38206 Tenerife, Spain..
    Babusiaux, C.
    Univ Paris Diderot, CNRS, Observ Paris, GERI, F-92190 Meudon, France..
    Bensby, T.
    Lund Observ, Dept Astron & Theoret Phys, S-22100 Lund, Sweden..
    Blomme, R.
    Observ Royal Belgique, B-1180 Brussels, Belgium..
    Bragaglia, A.
    Osservatorio Astron Bologna, INAF, I-40127 Bologna, Italy..
    Flaccomio, E.
    Osserv Astron Palermo, INAF, I-90134 Palermo, Italy..
    Francois, P.
    Univ Paris Diderot, CNRS, Observ Paris, GERI, F-92190 Meudon, France..
    Hambly, N.
    Univ Edinburgh, Inst Astron, Edinburgh EH9 3HJ, Midlothian, Scotland..
    Irwin, M.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Lanzafame, A. C.
    Univ Catania, Sez Astrofis, Dipartimento Fis & Astron, I-95123 Catania, Italy..
    Pancino, E.
    Osservatorio Astron Bologna, INAF, I-40127 Bologna, Italy.;ASI Sci Data Ctr, I-00133 Rome, Italy..
    Recio-Blanco, A.
    Univ Nice Sophia Antipolis, Observ Cote Azur, CNRS, Lab Lagrange,UMR 7293, F-06304 Nice 4, France..
    Smiljanic, R.
    Nicholas Copernicus Univ, Dept Astrophys, PL-87100 Torun, Poland..
    Van Eck, S.
    Univ Libre Bruxelles, Inst Astron & Astrophys, B-1050 Brussels, Belgium..
    Walton, N.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Bayo, A.
    Univ Valparaiso, Inst Fis & Astron, Valparaiso, Chile..
    Bergemann, M.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Carraro, G.
    European So Observ, Santiago 19, Chile..
    Costado, M. T.
    CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain..
    Damiani, F.
    Osserv Astron Palermo, INAF, I-90134 Palermo, Italy..
    Edvardsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Franciosini, E.
    Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy..
    Frasca, A.
    Osserv Astrofis Catania, INAF, I-95123 Catania, Italy..
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Hill, V.
    Univ Nice Sophia Antipolis, Observ Cote Azur, CNRS, Lab Lagrange,UMR 7293, F-06304 Nice 4, France..
    Hourihane, A.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Jofre, P.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Lardo, C.
    Liverpool John Moores Univ, Astrophys Res Inst, Liverpool L3 5RF, Merseyside, England..
    de Laverny, P.
    Univ Nice Sophia Antipolis, Observ Cote Azur, CNRS, Lab Lagrange,UMR 7293, F-06304 Nice 4, France..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Magrini, L.
    Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy..
    Marconi, G.
    European So Observ, Santiago 19, Chile..
    Martayan, C.
    European So Observ, Santiago 19, Chile..
    Masseron, T.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Monaco, L.
    Univ Andres Bello, Dept Ciencias Fis, Santiago 8370134, Chile..
    Morbidelli, L.
    Osserv Astrofis Arcetri, INAF, I-50125 Florence, Italy..
    Prisinzano, L.
    Osserv Astron Palermo, INAF, I-90134 Palermo, Italy..
    Sbordone, L.
    Millennium Inst Astrophys, Santiago 7820436, Chile.;Pontificia Univ Catolica Chile, Santiago 7820436, Chile..
    Sousa, S. G.
    Univ Porto, CAUP, Inst Astrofis & Ciencias Espaco, P-4150762 Oporto, Portugal..
    Worley, C. C.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    Zaggia, S.
    INAF Padova Observ, I-35122 Padua, Italy..
    The Gaia-ESO Survey: Empirical determination of the precision of stellar radial velocities and projected rotation velocities2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 580, article id A75Article in journal (Refereed)
    Abstract [en]

    Context. The Gaia-ESO Survey (GES) is a large public spectroscopic survey at the European Southern Observatory Very Large Telescope. Aims. A key aim is to provide precise radial velocities (RVs) and projected equatorial velocities (v sin i) for representative samples of Galactic stars, which will complement information obtained by the Gaia astrometry satellite. Methods. We present an analysis to empirically quantify the size and distribution of uncertainties in RV and v sin i using spectra from repeated exposures of the same stars. Results. We show that the uncertainties vary as simple scaling functions of signal-to-noise ratio (S/N) and v sin i, that the uncertainties become larger with increasing photospheric temperature, but that the dependence on stellar gravity, metallicity and age is weak. The underlying uncertainty distributions have extended tails that are better represented by Student's t-distributions than by normal distributions. Conclusions. Parametrised results are provided, which enable estimates of the RV precision for almost all GES measurements, and estimates of the v sin i precision for stars in young clusters, as a function of S/N, v sin i and stellar temperature. The precision of individual high S/N GES RV measurements is 0.22-0.26 km s(-1), dependent on instrumental configuration.

  • 27. Jacobson, Heather R.
    et al.
    Keller, Stefan
    Frebel, Anna
    Casey, Andrew R.
    Asplund, Martin
    Bessell, Michael S.
    Da Costa, Gary S.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Marino, Anna F.
    Norris, John E.
    Pena, Jose M.
    Schmidt, Brian P.
    Tisserand, Patrick
    Walsh, Jennifer M.
    Yong, David
    Yu, Qinsi
    High-Resolution Spectroscopic Study of Extremely Metal-Poor Star Candidates from the Skymapper Survey2015In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 807, no 2, article id 171Article in journal (Refereed)
    Abstract [en]

    The SkyMapper Southern Sky Survey is carrying out a search for the most metal-poor stars in the Galaxy. It identifies candidates by way of its unique filter set which allows for estimation of stellar atmospheric parameters. The set includes a narrow filter centered on the Ca II K 3933 angstrom line, enabling a robust estimate of stellar metallicity. Promising candidates are then confirmed with spectroscopy. We present the analysis of Magellan Inamori Kyocera Echelle high-resolution spectroscopy of 122 metal-poor stars found by SkyMapper in the first two years of commissioning observations. Forty-one stars have [Fe/H] <= -3.0. Nine have [Fe/H] <= -3.5, with three at [Fe/H] similar to -4. A 1D LTE abundance analysis of the elements Li, C, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Sr, Ba, and Eu shows these stars have [X/Fe] ratios typical of other halo stars. One star with low [X/Fe] values appears to be "Fe-enhanced," while another star has an extremely large [Sr/Ba] ratio: >2. Only one other star is known to have a comparable value. Seven stars are "CEMP-no" stars ([C/Fe] > 0.7, [Ba/Fe] < 0). 21 stars exhibit mild r-process element enhancements (0.3 <= [Eu/Fe] < 1.0), while four stars have [Eu/Fe] >= 1.0. These results demonstrate the ability to identify extremely metal-poor stars from SkyMapper photometry, pointing to increased sample sizes and a better characterization of the metal-poor tail of the halo metallicity distribution function in the future.

  • 28. Jofré, P.
    et al.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Soubiran, C.
    Blanco-Cuaresma, S.
    Masseron, T.
    Nordlander, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Chemin, L.
    Worley, C. C.
    Van Eck, S.
    Hourihane, A.
    Gilmore, G.
    Adibekyan, V.
    Bergemann, M.
    Cantat-Gaudin, T.
    Delgado-Mena, E.
    González Hernández, J. I.
    Guiglion, G.
    Lardo, C.
    de Laverny, P.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Magrini, L.
    Mikolaitis, S.
    Montes, D.
    Pancino, E.
    Recio-Blanco, A.
    Sordo, R.
    Sousa, S.
    Tabernero, H. M.
    Vallenari, A.
    Gaia FGK benchmark stars: abundances of α and iron-peak elements2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 582, article id A81Article in journal (Refereed)
    Abstract [en]

    Context. In the current era of large spectroscopic surveys of the Milky Way, reference stars for calibrating astrophysical parameters and chemical abundances are of paramount importance. Aims. We determine elemental abundances of Mg, Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni for our predefined set of Gaia FGK benchmark stars. Methods. By analysing high-resolution spectra with a high signal-to-noise ratio taken from several archive datasets, we combined results of eight different methods to determine abundances on a line-by-line basis. We performed a detailed homogeneous analysis of the systematic uncertainties, such as differential versus absolute abundance analysis. We also assessed errors that are due to non-local thermal equilibrium and the stellar parameters in our final abundances. Results. Our results are provided by listing final abundances and the different sources of uncertainties, as well as line-by-line and method-by-method abundances. Conclusions. The atmospheric parameters of the Gaia FGK benchmark stars are already being widely used for calibration of several pipelines that are applied to different surveys. With the added reference abundances of ten elements, this set is very suitable for calibrating the chemical abundances obtained by these pipelines.

  • 29.
    Karovicova, I.
    et al.
    Heidelberg Univ, Zentrum Astron, Konigstuhl 12, D-69117 Heidelberg, Germany.
    White, T. R.
    Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Nordlander, T.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, D-69117 Heidelberg, Germany.
    Casagrande, L.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Ireland, M. J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Huber, D.
    Univ Sydney, Sch Phys, SIfA, Sydney, NSW 2006, Australia;Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark;Univ Hawaii, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA;SETI Inst, 189 Bernardo Ave, Mountain View, CA 94043 USA.
    Creevey, O.
    Univ Cote Azur, OCA, Lab Lagrange, CNRS, BP 4229, F-06304 Nice, France.
    Mourard, D.
    Univ Cote Azur, OCA, Lab Lagrange, CNRS, BP 4229, F-06304 Nice, France.
    Schaefer, G. H.
    Georgia State Univ, Dept Phys & Astron, POB 5060, Atlanta, GA 30302 USA.
    Gilmore, G.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England.
    Chiavassa, A.
    Univ Cote Azur, OCA, Lab Lagrange, CNRS, BP 4229, F-06304 Nice, France.
    Wittkowski, M.
    European Southern Observ, Karl Schwarzschild Str 2, D-85748 Garching, Germany.
    Jofre, P.
    Univ Diego Portales, Nucleo Astron, Ave Ejercito 441, Santiago, Chile.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Thevenin, F.
    Univ Cote Azur, OCA, Lab Lagrange, CNRS, BP 4229, F-06304 Nice, France.
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Accurate effective temperatures of the metal-poor benchmark stars HD140283, HD122563, and HD103095 from CHARA interferometry2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 475, no 1, p. L81-L85Article in journal (Refereed)
    Abstract [en]

    Large stellar surveys of the MilkyWay require validation with reference to a set of 'benchmark' stars whose fundamental properties are well determined. For metal-poor benchmark stars, disagreement between spectroscopic and interferometric effective temperatures has called the reliability of the temperature scale into question. We present new interferometric measurements of three metal-poor benchmark stars, HD140283, HD122563, and HD103095, from which we determine their effective temperatures. The angular sizes of all the stars were determined from observations with the PAVO beam combiner at visible wavelengths at the CHARA array, with additional observations of HD103095 made with the VEGA instrument, also at the CHARA array. Together with photometrically derived bolometric fluxes, the angular diameters give a direct measurement of the effective temperature. For HD140283, we find theta(LD) = 0.324 +/- 0.005 mas, T-eff = 5787 +/- 48 K; for HD122563,theta(LD) = 0.926 +/- 0.011 mas, T-eff = 4636 +/- 37 K; and for HD103095,theta(LD) = 0.595 +/- 0.007 mas, T-eff = 5140 +/- 49 K. Our temperatures for HD140283 and HD103095 are hotter than the previous interferometric measurements by 253 and 322 K, respectively. We find good agreement between our temperatures and recent spectroscopic and photometric estimates. We conclude some previous interferometric measurements have been affected by systematic uncertainties larger than their quoted errors.

  • 30. Kordopatis, G.
    et al.
    Wyse, R. F. G.
    Gilmore, G.
    Recio-Blanco, A.
    de Laverny, P.
    Hill, V.
    Adibekyan, V.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Minchev, I.
    Famaey, B.
    Bensby, T.
    Feltzing, S.
    Guiglion, G.
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Mikolaitis, \v S.
    Schultheis, M.
    Vallenari, A.
    Bayo, A.
    Carraro, G.
    Flaccomio, E.
    Franciosini, E.
    Hourihane, A.
    Jofré, P.
    Koposov, S. E.
    Lardo, C.
    Lewis, J.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Magrini, L.
    Morbidelli, L.
    Pancino, E.
    Randich, S.
    Sacco, G. G.
    Worley, C. C.
    Zaggia, S.
    The Gaia-ESO Survey: characterisation of the [α/Fe] sequences in the Milky Way discs2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 582, article id A122Article in journal (Refereed)
    Abstract [en]

    Context. High-resolution spectroscopic surveys of stars indicate that the Milky Way thin and thick discs follow different paths in the chemical space defined by [alpha/Fe] vs. [Fe/H], possibly suggesting different formation mechanisms for each of these structures. Aims. We investigate, using the Gaia-ESO Survey internal Data-Release 2, the properties of the double sequence of the Milky Way discs, which are defined chemically as the high-alpha and low-alpha populations. We discuss their compatibility with discs defined by other means, such as metallicity, kinematics, or positions. Methods. This investigation uses two different approaches: in velocity space, for stars located in the extended solar neighbourhood; and, in chemical space, for stars at different ranges of Galactocentric radii and heights from the Galactic mid-plane. The separation we find in velocity space allows us to investigate, using a novel approach, the extent of metallicity of each of the two chemical sequences, without making any assumption about the shape of their metallicity distribution functions. Then, using the separation in chemical space, adopting the magnesium abundance as a tracer of the alpha-elements, we characterise the spatial variation of the slopes of the [alpha/Fe] [Fe/H] sequences for the thick and thin discs and the way in which the relative proportions of the two discs change across the Galaxy. Results. We find that the thick disc, defined as the stars tracing the high-alpha sequence, extends up to super-solar metallicities ([Fe/H] approximate to + 0.2 dex), and the thin disc, defined as the stars tracing the low-alpha sequence, extends at least down to [Fe/H] approximate to 0.8 dex, with hints pointing towards even lower values. Radial and vertical gradients in alpha-abundances are found for the thin disc, with mild spatial variations in its [alpha/Fe] [Fe/H] paths, whereas for the thick disc we do not detect any spatial variations of this kind. This is in agreement with results obtained recently from other high-resolution spectroscopic surveys. Conclusions. The small variations in the spatial [alpha/Fe] [Fe/H] paths of the thin disc do not allow us to distinguish between formation models of this structure. On the other hand, the lack of radial gradients and [alpha/Fe] [Fe/H] variations for the thick disc indicate that the mechanism responsible for the mixing of metals in the young Galaxy (e.g. radial stellar migration or turbulent gaseous disc) was more efficient before the (present) thin disc started forming.

  • 31.
    Kos, Janez
    et al.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia..
    Bland-Hawthor, Joss
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.;ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia..
    Freeman, Ken
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Buder, Sven
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Traven, Gregor
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia..
    De Silva, Gayandhi M.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.;Australian Astron Observ, N Ryde, NSW 2133, Australia..
    Sharma, Sanjib
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia..
    Asplund, Martin
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Duong, Ly
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Lin, Jane
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Martell, Sarah
    UNSW, Sch Phys, Sydney, NSW 2052, Australia..
    Simpson, Jeffrey D.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia..
    Stello, Dennis
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.;UNSW, Sch Phys, Sydney, NSW 2052, Australia.;Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, DK-8000 Aarhus C, Denmark..
    Zucker, Daniel B.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia..
    Zwitter, Tomaz
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia..
    Anguiano, Borja
    Univ Virginia, Dept Astron, Charlottesville, VA 22904 USA..
    Da Costa, Gary
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    D'Orazi, Valentina
    Osserv Astron Padova, INAF, Vicolo Osservatorio 5, I-35122 Padua, Italy..
    Horner, Jonathan
    Univ Southern Queensland, Computat Engn & Sci Res Ctr, Toowoomba, Qld 4350, Australia..
    Kafle, Prajwal R.
    Univ Western Australia M468, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia..
    Lewis, Geraint
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia..
    Munari, Ulisse
    Astron Observ Padova, INAF Natl Inst Astrophys, I-36012 Asiago, Italy..
    Nataf, David M.
    Johns Hopkins Univ, Ctr Astrophys Sci, Baltimore, MD 21218 USA.;Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA..
    Ness, Melissa
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Reid, Warren
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.;Western Sydney Univ, Locked Bag 1797, Penrith, NSW 2751, Australia..
    Schlesinger, Katie
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Ting, Yuan-Sen
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Wyse, Rosemary
    Johns Hopkins Univ, Ctr Astrophys Sci, Baltimore, MD 21218 USA.;Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA..
    The GALAH survey: chemical tagging of star clusters and new members in the Pleiades2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 4, p. 4612-4633Article in journal (Refereed)
    Abstract [en]

    The technique of chemical tagging uses the elemental abundances of stellar atmospheres to 'reconstruct' chemically homogeneous star clusters that have long since dispersed. The GALAH spectroscopic survey - which aims to observe one million stars using the Anglo-Australian Telescope - allows us to measure up to 30 elements or dimensions in the stellar chemical abundance space, many of which are not independent. How to find clustering reliably in a noisy high-dimensional space is a difficult problem that remains largely unsolved. Here, we explore t-distributed stochastic neighbour embedding (t-SNE) - which identifies an optimal mapping of a high-dimensional space into fewer dimensions - whilst conserving the original clustering information. Typically, the projection is made to a 2D space to aid recognition of clusters by eye. We show that this method is a reliable tool for chemical tagging because it can: (i) resolve clustering in chemical space alone, (ii) recover known open and globular clusters with high efficiency and low contamination, and (iii) relate field stars to known clusters. t-SNE also provides a useful visualization of a high-dimensional space. We demonstrate the method on a data set of 13 abundances measured in the spectra of 187 000 stars by the GALAH survey. We recover seven of the nine observed clusters (six globular and three open clusters) in chemical space with minimal contamination from field stars and low numbers of outliers. With chemical tagging, we also identify two Pleiades supercluster members (which we confirm kinematically), one as far as 6 degrees-one tidal radius away from the cluster centre.

  • 32.
    Kos, Janez
    et al.
    Univ Sydney, Sydney Inst Astron, Sch Phys A28, Sydney, NSW 2006, Australia..
    de Silva, Gayandhi
    Univ Sydney, Sydney Inst Astron, Sch Phys A28, Sydney, NSW 2006, Australia.;Macquarie Univ, AAO MQ, Sydney, NSW 2109, Australia..
    Buder, Sven
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.;Heidelberg Univ, Int Max Planck Res Sch Astron & Cosm Phys, Heidelberg, Germany..
    Bland-Hawthorn, Joss
    Univ Sydney, Sydney Inst Astron, Sch Phys A28, Sydney, NSW 2006, Australia.;ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia.;Univ Sydney, Sydney Astrophoton Instrumentat Labs, Sch Phys, A28, Camperdown, NSW 2006, Australia..
    Sharma, Sanjib
    Univ Sydney, Sydney Inst Astron, Sch Phys A28, Sydney, NSW 2006, Australia..
    Asplund, Martin
    ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia.;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    D'Orazi, Valentina
    Osserv Astron Padova, Inst Nazl Astrofis, Vicolo Osservatorio 5, I-35122 Padua, Italy..
    Duong, Ly
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Freeman, Ken
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Lewis, Geraint F.
    Univ Sydney, Sydney Inst Astron, Sch Phys A28, Sydney, NSW 2006, Australia..
    Lin, Jane
    ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia.;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany..
    Martell, Sarah L.
    MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.;UNSW, Sch Phys, Sydney, NSW 2052, Australia..
    Schlesinger, Katharine J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Simpson, Jeffrey D.
    UNSW, Sch Phys, Sydney, NSW 2052, Australia..
    Zucker, Daniel B.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia..
    Zwitter, Tomaz
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia..
    Bedding, Timothy R.
    Univ Sydney, Sydney Inst Astron, Sch Phys A28, Sydney, NSW 2006, Australia.;Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, DK-8000 Aarhus C, Denmark..
    Cotar, Klemen
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia..
    Horner, Jonathan
    Univ Southern Queensland, Div Res & Innovat, Toowoomba, Qld 4350, Australia..
    Nordlander, Thomas
    ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia.;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Stello, Denis
    UNSW, Sch Phys, Sydney, NSW 2052, Australia.;Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, DK-8000 Aarhus C, Denmark..
    Ting, Yuan-Sen
    Inst Adv Study, Princeton, NJ 08540 USA.;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA.;Observ Carnegie Inst Washington, 813 Santa Barbara St, Pasadena, CA 91101 USA..
    Traven, Gregor
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia..
    The GALAH survey and Gaia DR2: (non-)existence of five sparse high-latitude open clusters2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 480, no 4, p. 5242-5259Article in journal (Refereed)
    Abstract [en]

    Sparse open clusters can be found at high galactic latitudes where loosely populated clusters are more easily detected against the lower stellar background. Because most star formation takes place in the thin disc, the observed population of clusters far from the Galactic plane is hard to explain. We combined spectral parameters from the GALAH survey with the Gaia DR2 catalogue to study the dynamics and chemistry of five old sparse high-latitude clusters in more detail. We find that four of them (NGC 1252, NGC 6994, NGC 7772, NGC 7826) - originally classified in 1888 - are not clusters but are instead chance projections on the sky. Member stars quoted in the literature for these four clusters are unrelated in our multidimensional physical parameter space; the quoted cluster properties in the literature are therefore meaningless. We confirm the existence of visually similar NGC 1901 for which we provide a probabilistic membership analysis. An overdensity in three spatial dimensions proves to be enough to reliably detect sparse clusters, but the whole six-dimensional space must be used to identify members with high confidence, as demonstrated in the case of NGC 1901.

  • 33.
    Lind, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Germany..
    Amarsi, A. M.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.;Australian Natl Univ, Res Sch Astron & Astrophys, Cotter Rd, Canberra, ACT 2611, Australia..
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Cotter Rd, Canberra, ACT 2611, Australia..
    Barklem, Paul S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Bautista, M.
    Western Michigan Univ, Dept Phys, Kalamazoo, MI 49008 USA..
    Bergemann, M.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Collet, R.
    Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Kiselman, D.
    Stockholm Univ, Albanova Univ Ctr, Dept Astron, Inst Solar Phys, SE-10691 Stockholm, Sweden..
    Leenaarts, J.
    Stockholm Univ, Albanova Univ Ctr, Dept Astron, Inst Solar Phys, SE-10691 Stockholm, Sweden..
    Pereira, T. M. D.
    Univ Oslo, Inst Theoret Astrophys, POB 1029, N-0315 Oslo, Norway..
    Non-LTE line formation of Fe in late-type stars - IV. Modelling of the solar centre-to-limb variation in 3D2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 468, no 4, p. 4311-4322Article in journal (Refereed)
    Abstract [en]

    Our ability to model the shapes and strengths of iron lines in the solar spectrum is a critical test of the accuracy of the solar iron abundance, which sets the absolute zero-point of all stellar metallicities. We use an extensive 463-level Fe atom with new photoionization cross-sections for Fe I and quantum mechanical calculations of collisional excitation and charge transfer with neutral hydrogen; the latter effectively remove a free parameter that has hampered all previous line formation studies of Fe in non-local thermodynamic equilibrium (NLTE). For the first time, we use realistic 3D NLTE calculations of Fe for a quantitative comparison to solar observations. We confront our theoretical line profiles with observations taken at different viewing angles across the solar disc with the Swedish 1-m Solar Telescope. We find that 3D modelling well reproduces the observed centre-to-limb behaviour of spectral lines overall, but highlight aspects that may require further work, especially cross-sections for inelastic collisions with electrons. Our inferred solar iron abundance is log(epsilon(Fe)) = 7.48 +/- 0.04 dex.

  • 34.
    Lind, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Koposov, S. E.
    Battistini, C.
    Marino, A. F.
    Ruchti, G.
    Serenelli, A.
    Worley, C. C.
    Alves-Brito, A.
    Asplund, M.
    Barklem, Paul S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Bensby, T.
    Bergemann, M.
    Blanco-Cuaresma, S.
    Bragaglia, A.
    Edvardsson, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Feltzing, S.
    Gruyters, Pieter
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Jofre, P.
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Nordlander, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Ryde, N.
    Soubiran, C.
    Gilmore, G.
    Randich, S.
    Ferguson, A. M. N.
    Jeffries, R. D.
    Vallenari, A.
    Allende Prieto, C.
    Pancino, E.
    Recio-Blanco, A.
    Romano, D.
    Smiljanic, R.
    Bellazzini, M.
    Damiani, F.
    Hill, V.
    de laverny, P.
    Jackson, R. J.
    Lardo, C.
    Zaggia, S.
    The Gaia-ESO Survey: A globular cluster escapee in the Galactic halo2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 575, article id L12Article in journal (Refereed)
    Abstract [en]

    A small fraction of the halo field is made up of stars that share the light element (Z <= 13) anomalies characteristic of second generation globular cluster (GC) stars. The ejected stars shed light on the formation of the Galactic halo by tracing the dynamical history of the clusters, which are believed to have once been more massive. Some of these ejected stars are expected to show strong Al enhancement at the expense of shortage of Mg, but until now no such star has been found. We search for outliers in the Mg and Al abundances of the few hundreds of halo field stars observed in the first eighteen months of the Gaia-ESO public spectroscopic survey. One halo star at the base of the red giant branch, here referred to as 22593757-4648029 is found to have [Mg/Fe] = -0.36 +/- 0.04 and [Al/Fe] = 0.99 +/- 0.08, which is compatible with the most extreme ratios detected in GCs so far. We compare the orbit of 22593757-4648029 to GCs of similar metallicity and find it unlikely that this star has been tidally stripped with low ejection velocity from any of the clusters. However, both chemical and kinematic arguments render it plausible that the star has been ejected at high velocity from the anomalous GC omega Centauri within the last few billion years. We cannot rule out other progenitor GCs, because some may have disrupted fully, and the abundance and orbital data are inadequate for many of those that are still intact.

  • 35.
    Marino, A. F.
    et al.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia;Univ Padua, Dipartimento Fis & Astron Galileo Galilei, Vicolo Osservatorio 3, IT-35122 Padua, Italy;CISAS, Ctr Ateneo Studi & Attivita Spaziali Giuseppe Col, IT-35131 Padua, Italy.
    Da Costa, G. S.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Casey, A. R.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia;Monash Univ, Sch Phys & Astron, Wellington Rd, Clayton, Vic 3800, Australia;Monash Univ, Fac Informat Technol, Wellington Rd, Clayton, Vic 3800, Australia.
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT, Australia.
    Bessell, M. S.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Frebel, A.
    MIT, Dept Phys, Cambridge, MA 02139 USA;MIT, Kavli Inst Astrophys & Space Res, Cambridge, MA 02139 USA.
    Keller, S. C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Mackey, A. D.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Murphy, S. J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia;Univ New South Wales, Sch Phys Environm & Math Sci, Canberra, ACT 2600, Australia.
    Nordlander, T.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT, Australia.
    Norris, J. E.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Schmidt, B. P.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Yong, D.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Keck HIRES spectroscopy of SkyMapper commissioning survey candidate extremely metal-poor stars2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 485, no 4, p. 5153-5167Article in journal (Refereed)
    Abstract [en]

    We present results from the analysis of high-resolution spectra obtained with the Keck HIRES spectrograph for a sample of 17 candidate extremely metal-poor (EMP) stars originally selected from commissioning data obtained with the SkyMapper telescope. Fourteen of the stars have not been observed previously at high dispersion. Three have [Fe/H] <= -3.0, while the remainder, with two more metal-rich exceptions, have -3.0 <= [Fe/H] <= -2.0 dex. Apart from Fe, we also derive abundances for the elements C, N, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, and Zn, and for n-capture elements Sr, Ba, and Eu. None of the current sample of stars is found to be carbon-rich. In general, our chemical abundances follow previous trends found in the literature, although we note that two of the most metal-poor stars show very low [Ba/Fe] (similar to-1.7) coupled with low [Sr/Ba] (similar to-0.3). Such stars are relatively rare in the Galactic halo. One further star, and possibly two others, meet the criteria for classification as a r-I star. This study, together with that of Jacobson et al. (2015), completes the outcomes of the SkyMapper commissioning data survey for EMP stars.

  • 36. Marino, A. F.
    et al.
    Milone, A. P.
    Karakas, A. I.
    Casagrande, L.
    Yong, D.
    Shingles, L.
    Da Costa, G.
    Norris, J. E.
    Stetson, P. B.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Asplund, M.
    Collet, R.
    Jerjen, H.
    Sbordone, L.
    Aparicio, A.
    Cassisi, S.
    Iron and s-elements abundance variations in NGC 5286: comparison with 'anomalous' globular clusters and Milky Way satellites2015In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 450, no 1, p. 815-845Article in journal (Refereed)
    Abstract [en]

    We present a high-resolution spectroscopic analysis of 62 red giants in the Milky Way globular cluster (GC) NGC 5286. We have determined abundances of representative light proton-capture, a, Fe-peak and neutron-capture element groups, and combined them with photometry of multiple sequences observed along the colour-magnitude diagram. Our principal results are: (i) a broad, bimodal distribution in s-process element abundance ratios, with two main groups, the s-poor and s-rich groups; (ii) substantial star-to-star Fe variations, with the s-rich stars having higher Fe, e.g. <[Fe/H]>(s-rich) - <[Fe/H]>(s-poor) similar to 0.2 dex; and (iii) the presence of O-Na-Al (anti) correlations in both stellar groups. We have defined a new photometric index, c(BVI) = (B - V) -(V - I), to maximize the separation in the colour-magnitude diagram between the two stellar groups with different Fe and s-element content, and this index is not significantly affected by variations in light elements (such as the O-Na anticorrelation). The variations in the overall metallicity present in NGC 5286 add this object to the class of anomalous GCs. Furthermore, the chemical abundance pattern of NGC 5286 resembles that observed in some of the anomalous GCs, e.g. M 22, NGC 1851, M 2, and the more extreme omega Centauri, that also show internal variations in s-elements, and in light elements within stars with different Fe and s-elements content. In view of the common variations in s-elements, we propose the term s-Fe-anomalous GCs to describe this sub-class of objects. The similarities in chemical abundance ratios between these objects strongly suggest similar formation and evolution histories, possibly associated with an origin in tidally disrupted dwarf satellites.

  • 37.
    Martell, S. L.
    et al.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia..
    Sharma, S.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia..
    Buder, S.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Duong, L.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Schlesinger, K. J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Simpson, J.
    Australian Astron Observ, N Ryde, NSW 2113, Australia..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Ness, M.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Marshall, J. P.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.;Univ New South Wales, Australian Ctr Astrobiol, Sydney, NSW 2052, Australia..
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Bland-Hawthorn, J.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia..
    Casey, A. R.
    Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England..
    De Silva, G.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia..
    Freeman, K. C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Kos, J.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia..
    Lin, J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Zucker, D. B.
    Australian Astron Observ, N Ryde, NSW 2113, Australia.;Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.;Macquarie Univ, Res Ctr Astron Astrophys & Astrophoton, Sydney, NSW 2109, Australia..
    Zwitter, T.
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia..
    Anguiano, B.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.;Macquarie Univ, Res Ctr Astron Astrophys & Astrophoton, Sydney, NSW 2109, Australia..
    Bacigalupo, C.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.;Macquarie Univ, Res Ctr Astron Astrophys & Astrophoton, Sydney, NSW 2109, Australia..
    Carollo, D.
    Casagrande, L.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Da Costa, G. S.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Horner, J.
    Huber, D.
    Hyde, E. A.
    Australian Astron Observ, N Ryde, NSW 2113, Australia..
    Kafle, P. R.
    Lewis, G. F.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia..
    Nataf, D.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia..
    Navin, C. A.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.;Macquarie Univ, Res Ctr Astron Astrophys & Astrophoton, Sydney, NSW 2109, Australia..
    Stello, D.
    Univ Sydney, Sydney Inst Astron, Sch Phys, A28, Sydney, NSW 2006, Australia..
    Tinney, C. G.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.;Univ New South Wales, Australian Ctr Astrobiol, Sydney, NSW 2052, Australia..
    Watson, F. G.
    Australian Astron Observ, N Ryde, NSW 2113, Australia..
    Wittenmyer, R.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.;Univ New South Wales, Australian Ctr Astrobiol, Sydney, NSW 2052, Australia..
    The GALAH survey: observational overview and Gaia DR1 companion2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 465, no 3, p. 3203-3219Article in journal (Refereed)
    Abstract [en]

    The Galactic Archaeology with HERMES (GALAH) survey is amassive observational project to trace the MilkyWay's history of star formation, chemical enrichment, stellar migration and minor mergers. Using high-resolution (R similar or equal to 28 000) spectra, taken with the High Efficiency and Resolution Multi- Element Spectrograph (HERMES) instrument at the Anglo-Australian Telescope, GALAH will determine stellar parameters and abundances of up to 29 elements for up to one million stars. Selecting targets from a colour-unbiased catalogue built from 2MASS, APASS and UCAC4 data, we expect to observe dwarfs at 0.3-3 kpc and giants at 1-10 kpc. This enables a thorough local chemical inventory of the Galactic thin and thick discs, and also captures smaller samples of the bulge and halo. In this paper, we present the plan, process and progress as of early 2016 for GALAH survey observations. In our first two years of survey observing we have accumulated the largest high-quality spectroscopic data set at this resolution, over 200 000 stars. We also present the first public GALAH data catalogue: stellar parameters (T-eff, log(g), [ Fe/ H], [ alpha/ Fe]), radial velocity, distance modulus and reddening for 10 680 observations of 9860 Tycho-2 stars, 7894 of which are included in the first Gaia data release.

  • 38.
    Martinez Osorio, Yeisson Fabian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Barklem, Paul
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Belyaev, A. K.
    Spielfiedel, A.
    Guitou, M.
    Feautrier, N.
    Mg line formation in late-type stellar atmospheres: I. The model atom2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 579, article id A53Article in journal (Refereed)
    Abstract [en]

    Context. Magnesium is an element of significant astrophysical importance, often traced in late-type stars using lines of neutral magnesium, which is expected to be subject to departures from local thermodynamic equilibrium (LTE). The importance of Mg, together with the unique range of spectral features in late-type stars probing different parts of the atom, as well as its relative simplicity from an atomic physics point of view, makes it a prime target and test bed for detailed ab initio non-LTE modelling in stellar atmospheres. Previous non-LTE modelling of spectral line formation has, however, been subject to uncertainties due to lack of accurate data for inelastic collisions with electrons and hydrogen atoms.

    Aims. In this paper we build and test a Mg model atom for spectral line formation in late-type stars with new or recent inelastic collision data and no associated free parameters. We aim to reduce these uncertainties and thereby improve the accuracy of Mg non-LTE modelling in late-type stars.

    Methods. For the low-lying states of Mg I, electron collision data were calculated using the R-matrix method. Hydrogen collision data, including charge transfer processes, were taken from recent calculations by some of us. Calculations for collisional broadening by neutral hydrogen were also performed where data were missing. These calculations, together with data from the literature, were used to build a model atom. This model was then employed in the context of standard non-LTE modelling in 1D (including average 3D) model atmospheres in a small set of stellar atmosphere models. First, the modelling was tested by comparisons with observed spectra of benchmark stars with well-known parameters. Second, the spectral line behaviour and uncertainties were explored by extensive experiments in which sets of collisional data were changed or removed.

    Results. The modelled spectra agree well with observed spectra from benchmark stars, showing much better agreement with line profile shapes than with LTE modelling. The line-to-line scatter in the derived abundances shows some improvements compared to LTE (where the cores of strong lines must often be ignored), particularly when coupled with averaged 3D models. The observed Mg emission features at 7 and 12 mu m in the spectra of the Sun and Arcturus, which are sensitive to the collision data, are reasonably well reproduced. Charge transfer with H is generally important as a thermalising mechanism in dwarfs, but less so in giants. Excitation due to collisions with H is found to be quite important in both giants and dwarfs. The R-matrix calculations for electron collisions also lead to significant differences compared to when approximate formulas are employed. The modelling predicts non-LTE abundance corrections Delta A(Mg)(NLTE-LTE) in dwarfs, both solar metallicity and metal-poor, to be very small (of order 0.01 dex), even smaller than found in previous studies. In giants, corrections vary greatly between lines, but can be as large as 0.4 dex.

    Conclusions. Our results emphasise the need for accurate data of Mg collisions with both electrons and H atoms for precise non-LTE predictions of stellar spectra, but demonstrate that such data can be calculated and that ab initio non-LTE modelling without resort to free parameters is possible. In contrast to Li and Na, where only the introduction of charge transfer processes has led to differences with respect to earlier non-LTE modelling, the more complex case of Mg finds changes due to improvements in the data for collisional excitation by electrons and hydrogen atoms, as well as due to the charge transfer processes. Grids of departure coefficients and abundance corrections for a range of stellar parameters are planned for a forthcoming paper.

  • 39.
    Nordlander, T.
    et al.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia;ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia.
    Bessell, M. S.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia;ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia.
    Da Costa, G. S.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Mackey, A. D.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia;ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia.
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia;ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia.
    Casey, A. R.
    Monash Univ, Sch Phys & Astron, Clayton, Vic 3800, Australia;Monash Univ, Fac Informat Technol, Clayton, Vic 3800, Australia.
    Chiti, A.
    MIT, Dept Phys, Cambridge, MA 02139 USA;MIT, Kavli Inst Astrophys & Space Res, Cambridge, MA 02139 USA.
    Ezzeddine, R.
    MIT, Dept Phys, Cambridge, MA 02139 USA;MIT, Kavli Inst Astrophys & Space Res, Cambridge, MA 02139 USA;Joint Inst Nucl Astrophys, Ctr Evolut Elements, E Lansing, MI 48824 USA.
    Frebel, A.
    MIT, Dept Phys, Cambridge, MA 02139 USA;MIT, Kavli Inst Astrophys & Space Res, Cambridge, MA 02139 USA;Joint Inst Nucl Astrophys, Ctr Evolut Elements, E Lansing, MI 48824 USA.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany;.
    Marino, A. F.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia;Univ Padua, Dipartimento Fis & Astron Galileo Galilei, Vicolo Osservatorio 3, I-35122 Padua, Italy.
    Murphy, S. J.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia;Univ New South Wales, Sch Sci, Canberra, ACT 2600, Australia.
    Norris, J. E.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Schmidt, B. P.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Yong, D.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia;ARC Ctr Excellence All Sky Astrophys 3 Dimens AST, Canberra, ACT, Australia.
    The lowest detected stellar Fe abundance: the halo star SMSS J160540.18-144323.12019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 488, no 1, p. L109-L113Article in journal (Refereed)
    Abstract [en]

    We report the discovery of SMSS J160540.18-144323.1, a new ultra metal-poor halo star discovered with the SkyMapper telescope. We measure [Fe/H] = -6.2 +/- 0.2 (1D LTE), the lowest ever detected abundance of iron in a star. The star is strongly carbon-enhanced, [C/Fe] = 3.9 +/- 0.2, while other abundances are compatible with an alpha-enhanced solar-like pattern with [Ca/Fe] = 0.4 +/- 0.2, [Mg/Fe] = 0.6 +/- 0.2, [Ti/Fe] = 0.8 +/- 0.2, and no significant s- or r-process enrichment, [Sr/Fe] < 0.2 and [Ba/Fe] < 1.0 (3 sigma limits). Population III stars exploding as fallback supernovae may explain both the strong carbon enhancement and the apparent lack of enhancement of odd-Z and neutron-capture element abundances. Grids of supernova models computed for metal-free progenitor stars yield good matches for stars of about 10 M circle dot imparting a low kinetic energy on the supernova ejecta, while models for stars more massive than roughly 20 M circle dot are incompatible with the observed abundance pattern.

  • 40.
    Nordlander, Thomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Amarsi, A. M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany.
    Asplund, M.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.
    Barklem, Paul S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Casey, A. R.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England.
    Collet, R.
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia.; Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Leenaarts, J.
    Stockholm Univ, Inst Solar Phys, S-10691 Stockholm, Sweden.
    3D NLTE Analysis of the Most Iron-Deficient Star, SMSS0313-67082017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 597, article id A6Article in journal (Refereed)
    Abstract [en]

    Context. Models of star formation in the early universe require a detailed understanding of accretion, fragmentation and radiative feedback in metal-free molecular clouds. Different simulations predict different initial mass functions of the first stars, ranging from predominantly low-mass (0.1-10 Msol), to massive (10-100 Msol), or even supermassive (100-1000 Msol). The mass distribution of the first stars should lead to unique chemical imprints on the low-mass second and later generation metal-poor stars still in existence. The chemical composition of SMSS0313-6708, which has the lowest abundances of Ca and Fe of any star known, indicates it was enriched by a single massive supernova.

    Aims. The photospheres of metal-poor stars are relatively transparent in the UV, which may lead to large three-dimensional (3D) effects as well as departures from local thermodynamical equilibrium (LTE), even for weak spectral lines. If 3D effects and departures from LTE (NLTE) are ignored or treated incorrectly, errors in the inferred abundances may significantly bias the inferred properties of the polluting supernovae. We redetermine the chemical composition of SMSS0313-6708 by means of the most realistic methods available, and compare the results to predicted supernova yields.

    Methods. A 3D hydrodynamical Stagger model atmosphere and 3D NLTE radiative transfer were applied to obtain accurate abundances for Li, Na, Mg, Al, Ca and Fe. The model atoms employ realistic collisional rates, with no calibrated free parameters.

    Results. We find significantly higher abundances in 3D NLTE than 1D LTE by 0.8 dex for Fe, and 0.5 dex for Mg, Al and Ca, while Li and Na are unaffected to within 0.03 dex. In particular, our upper limit for [Fe/H] is now a factor ten larger, at [Fe/H] < -6.53 (3 sigma), than previous estimates based on <3D> NLTE (i.e., using averaged 3D models). This higher estimate is due to a conservative upper limit estimation, updated NLTE data, and 3D-<3D> NLTE differences, all of which lead to a higher abundance determination.

    Conclusions. We find that supernova yields for models in a wide range of progenitor masses reproduce the revised chemical composition. In addition to massive progenitors of 20-60 Msol exploding with low energies (1-2 B, where 1 B = 10^51 erg), we also find good fits for progenitors of 10 Msol, with very low explosion energies (<1 B). We cannot reconcile the new abundances with supernovae or hypernovae with explosion energies above 2.5 B, nor with pair-instability supernovae. 

  • 41.
    Nordlander, Thomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Research School of Astronomy and Astrophysics, Australian National University, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max-Planck-Institut für Astronomie, Heidelberg, Germany.
    Non-LTE aluminium abundances in late-type stars2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 607, article id A75Article in journal (Refereed)
    Abstract [en]

    Aims. Aluminium plays a key role in studies of the chemical enrichment of the Galaxy and of globular clusters. However, strong deviations from LTE (non-LTE) are known to significantly affect the inferred abundances in giant and metal-poor stars.

    Methods. We present NLTE modeling of aluminium using recent and accurate atomic data, in particular utilizing new transition rates for collisions with hydrogen atoms, without the need for any astrophysically calibrated parameters. For the first time, we perform 3D NLTE modeling of aluminium lines in the solar spectrum. We also compute and make available extensive grids of abundance corrections for lines in the optical and near-infrared using one-dimensional model atmospheres, and apply grids of precomputed departure coefficients to direct line synthesis for a set of benchmark stars with accurately known stellar parameters.

    Results. Our 3D NLTE modeling of the solar spectrum reproduces observed center-to-limb variations in the solar spectrum of the 7835 Å line as well as the mid-infrared photospheric emission line at 12.33 μm. We infer a 3D NLTE solar photospheric abundance of A(Al) = 6.43 ± 0.03, in perfect agreement with the meteoritic abundance. We find that abundance corrections vary rapidly with stellar parameters; for the 3961 Å resonance line, corrections are positive and may be as large as +1 dex, while corrections for subordinate lines generally have positive sign for warm stars but negative for cool stars. Our modeling reproduces the observed line profiles of benchmark K-giants, and we find abundance corrections as large as −0.4 dex for Arcturus. Our analyses of four metal-poor benchmark stars yield consistent abundances between the 3961 Å resonance line and lines in the UV, optical and near-infrared regions. Finally, we discuss implications for the galactic chemical evolution of aluminium. 

  • 42.
    Osorio, Y.
    et al.
    Inst Astrofis Canarias, Tenerife 38205, Spain;Univ La Laguna, E-38206 Tenerife, Spain.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. Max Plank Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Barklem, Paul S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Prieto, C. Allende
    Inst Astrofis Canarias, Tenerife 38205, Spain;Univ La Laguna, E-38206 Tenerife, Spain.
    Zatsarinny, O.
    Drake Univ, Dept Phys & Astron, Des Moines, IA 50311 USA.
    Ca line formation in late-type stellar atmospheres: I. The model atom2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 623, article id A103Article in journal (Refereed)
    Abstract [en]

    Context

    Departures from local thermodynamic equilibrium (LTE) distort the calcium abundance derived from stellar spectra in various ways, depending on the lines used and the stellar atmospheric parameters. The collection of atomic data adopted in non-LTE (NLTE) calculations must be sufficiently complete and accurate.

    Aims

    We derive NLTE abundances from high-quality observations and reliable stellar parameters using a model atom built afresh for this work, and check the consistency of our results over a wide wavelength range with transitions of atomic and singly ionised calcium.

    Methods

    We built and tested Cat and Can model atoms with state-of-the-art radiative and collisional data, and tested their performance deriving the Ca abundance in three benchmark stars: Procyon, the Sun, and Arcturus. We have excellent-quality observations and accurate stellar parameters for these stars. Two methods to derive the LTE/NLTE abundances were used and compared. The LTE/NLTE centre-to-limb variation (CLV) of Ca lines in the Sun was also investigated.

    Results

    The two methods used give similar results in all three stars. Several discrepancies found in LTE do not appear in our NLTE results; in particular the agreement between abundances in the visual and infra-red (IR) and the Cat and Can ionisation balance is improved overall, although substantial line-to-line scatter remains. The CLV of the calcium lines around 6165 angstrom can be partially reproduced. We suspect differences between our modelling and CLV results are due to inhomogeneities in the atmosphere that require 3D modelling.

  • 43.
    Quillen, Alice C.
    et al.
    Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA.
    De Silva, Gayandhi
    Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia;Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.
    Sharma, Sanjib
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.
    Hayden, Michael
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Australian Res Council, Ctr Excellence All Sky Astrophys Dimens 3 ASTRO 3, Canberra, ACT 72611, Australia.
    Freeman, Ken
    Australian Natl Univ, Res Sch Astron & Astrophys, Cotter Rd, Canberra, ACT 72611, Australia.
    Bland-Hawthorn, Joss
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Univ Calif Berkeley, Dept Astron, Campbell Hall, Berkeley, CA 94720 USA;Australian Res Council, Ctr Excellence All Sky Astrophys Dimens 3 ASTRO 3, Canberra, ACT 72611, Australia.
    Zerjal, Marusa
    Australian Natl Univ, Res Sch Astron & Astrophys, Cotter Rd, Canberra, ACT 72611, Australia.
    Asplund, Martin
    Australian Natl Univ, Res Sch Astron & Astrophys, Cotter Rd, Canberra, ACT 72611, Australia;Australian Res Council, Ctr Excellence All Sky Astrophys Dimens 3 ASTRO 3, Canberra, ACT 72611, Australia.
    Buder, Sven
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    D'Orazi, Valentina
    Ist Nazl Astrofis, Osservatorio Astron Padova, Vicolo Osservatorio 5, I-35122 Padua, Italy.
    Duong, Ly
    Australian Natl Univ, Res Sch Astron & Astrophys, Cotter Rd, Canberra, ACT 72611, Australia.
    Kos, Janez
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.
    Lin, Jane
    Australian Natl Univ, Res Sch Astron & Astrophys, Cotter Rd, Canberra, ACT 72611, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Martell, Sarah
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Schlesinger, Katharine
    Australian Natl Univ, Res Sch Astron & Astrophys, Cotter Rd, Canberra, ACT 72611, Australia.
    Simpson, Jeffrey D.
    Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia.
    Zucker, Daniel B.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia;Macquarie Univ, Res Ctr Astron Astrophys & Astrophoton, Sydney, NSW 2109, Australia.
    Zwitter, Tomaz
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Anguiano, Borja
    Univ Virginia, Dept Astron, POB 400325, Charlottesville, VA 22904 USA;Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.
    Carollo, Daniela
    Ist Nazl Astrofis, Via Osservatorio 20, I-10025 Pino Torinese, Italy;Australian Res Council, Ctr Excellence All Sky Astrophys Dimens 3 ASTRO 3, Canberra, ACT 72611, Australia.
    Casagrande, Luca
    Australian Natl Univ, Res Sch Astron & Astrophys, Cotter Rd, Canberra, ACT 72611, Australia.
    Cotar, Klemen
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Cottrell, Peter L.
    Univ Canterbury, Sch Phys & Chem Sci, Christchurch 8140, New Zealand;Monash Univ, Sch Phys & Astron, Monash Ctr Astrophys, Clayton, Vic 3800, Australia.
    Ireland, Michael
    Australian Natl Univ, Res Sch Astron & Astrophys, Cotter Rd, Canberra, ACT 72611, Australia.
    Kafle, Prajwal R.
    Univ Western Australia, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia.
    Horner, Jonathan
    Univ Southern Queensland, Div Res & Innovat, Toowoomba, Qld 4350, Australia.
    Lewis, Geraint F.
    Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia.
    Nataf, David M.
    Johns Hopkins Univ, Ctr Astrophys Sci, Baltimore, MD 21218 USA;Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    Ting, Yuan-Sen
    Observ Carnegie Inst Washington, 813 Santa Barbara St, Pasadena, CA 91101 USA;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA;Inst Adv Study, Princeton, NJ 08540 USA.
    Watson, Fred
    Australian Astron Observ, 105 Delhi Rd, N Ryde, NSW 2113, Australia.
    Wittenmyer, Rob
    Univ New South Wales, Australian Ctr Astrobiol, Sydney, NSW 2052, Australia;Univ Southern Queensland, Computat Engn & Sci Res Ctr, Toowoomba, Qld 4350, Australia.
    Wyse, Rosemary
    Johns Hopkins Univ, Ctr Astrophys Sci, Baltimore, MD 21218 USA;Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    The GALAH survey: stellar streams and how stellar velocity distributions vary with Galactic longitude, hemisphere, and metallicity2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 478, no 1, p. 228-254Article in journal (Refereed)
    Abstract [en]

    Using GALAH (GALactic Archaeology with HERMES) survey data of nearby stars, we look at how structure in the planar (u, v) velocity distribution depends on metallicity and on viewing direction within the Galaxy. In nearby stars with distance d less than or similar to 1 kpc, the Hercules stream is most strongly seen in higher metallicity stars [Fe/H] > 0.2. The Hercules stream peak v value depends on viewed galactic longitude, which we interpret as due to the gap between the stellar stream and more circular orbits being associated with a specific angular momentum value of about 16.40 km s(-1) kpc. The association of the gap with a particular angular momentum value supports a bar resonant model for the Hercules stream. Moving groups previously identified in Hipparcos (High Precision Parallax COllecting Satellite) observations are easiest to see in stars nearer than 250 pc, and their visibility and peak velocities in the velocity distributions depends on both viewing direction (galactic longitude and hemisphere) and metallicity. We infer that there is fine structure in local velocity distributions that varies over distances of a few hundred pc in the Galaxy.

  • 44.
    Reggiani, Henrique
    et al.
    Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, IAG, Dept Astron, Rua Matao 1226,Cidade Univ, BR-05508900 Sao Paulo, SP, Brazil;Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Amarsi, Anish M.
    Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany.
    Barklem, Paul S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Zatsarinny, Oleg
    Drake Univ, Dept Phys & Astron, Des Moines, IA 50311 USA.
    Bartschat, Klaus
    Drake Univ, Dept Phys & Astron, Des Moines, IA 50311 USA.
    Fursa, Dmitry, V
    Curtin Inst Computat, Kent St, Perth, WA 6102, Australia;Dept Phys & Astron, Kent St, Perth, WA 6102, Australia.
    Bray, Igor
    Curtin Inst Computat, Kent St, Perth, WA 6102, Australia;Dept Phys & Astron, Kent St, Perth, WA 6102, Australia.
    Spina, Lorenzo
    Monash Univ, Sch Phys & Astron, Monash Ctr Astrophys, Clayton, Vic 3800, Australia.
    Melendez, Jorge
    Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, IAG, Dept Astron, Rua Matao 1226,Cidade Univ, BR-05508900 Sao Paulo, SP, Brazil.
    Non-LTE analysis of K I in late-type stars2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 627, article id A177Article in journal (Refereed)
    Abstract [en]

    Context. Older models of Galactic chemical evolution (GCE) predict [K/Fe] ratios as much as 1 dex lower than those inferred from stellar observations. Abundances of potassium are mainly based on analyses of the 7698 angstrom resonance line, and the discrepancy between GCE models and observations is in part caused by the assumption of local thermodynamic equilibrium (LTE) in spectroscopic analyses. Aims. We study the statistical equilibrium of K I, focusing on the non-LTE effects on the 7698 angstrom line. We aim to determine how non-LTE abundances of potassium can improve the analysis of its chemical evolution, and help to constrain the yields of GCE models. Methods. We construct a new model K I atom that employs the most up-to-date atomic data. In particular, we calculate and present inelastic e+K collisional excitation cross-sections from the convergent close-coupling (CCC) and the B-Spline R-matrix (BSR) methods, and H+K collisions from the two-electron model (LCAO). We constructed a fine, extended grid of non-LTE abundance corrections based on 1D MARCS models that span 4000 < T-eff/K < 8000, 0.50 < log g < 5.00, -5.00 < [Fe/H] < +0.50, and applied the corrections to potassium abundances extracted from the literature. Results. In concordance with previous studies, we find severe non-LTE effects in the 7698 angstrom line. The line is stronger in non-LTE and the abundance corrections can reach approximately -0.7 dex for solar-metallicity stars such as Procyon. We determine potassium abundances in six benchmark stars, and obtain consistent results from different optical lines. We explore the effects of atmospheric inhomogeneity by computing for the first time a full 3D non-LTE stellar spectrum of K I lines for a test star. We find that 3D modeling is necessary to predict a correct shape of the resonance 7698 angstrom line, but the line strength is similar to that found in 1D non-LTE. Conclusions. Our non-LTE abundance corrections reduce the scatter and change the cosmic trends of literature potassium abundances. In the regime [Fe/H] less than or similar to -1.0 the non-LTE abundances show a good agreement with the GCE model with yields from rotating massive stars. The reduced scatter of the non-LTE corrected abundances of a sample of solar twins shows that line-by-line differential analysis techniques cannot fully compensate for systematic LTE modelling errors; the scatter introduced by such errors introduces a spurious dispersion to K evolution.

  • 45.
    Rojas-Arriagada, A.
    et al.
    Univ Cote Azur, Lab Lagrange, Observ Cote Azur, CS 34229, F-06304 Nice, France.;Pontificia Univ Catolica Chile, Fac Fis, Inst Astrofis, Av Vicuna Mackenna 4860, Santiago, Chile.;Millennium Inst Astrophys, Av Vicuna Mackenna 4860, Santiago 7820436, Chile..
    Recio-Blanco, A.
    Univ Cote Azur, Lab Lagrange, Observ Cote Azur, CS 34229, F-06304 Nice, France..
    de laverny, P.
    Univ Cote Azur, Lab Lagrange, Observ Cote Azur, CS 34229, F-06304 Nice, France..
    Mikolaitis, S.
    Vilnius Univ, Inst Theoret Phys & Astron, A Gostauto 12, LT-01108 Vilnius, Lithuania..
    Matteucci, F.
    Univ Trieste, Dipartimento Fis, Sez Astron, Via GB Tiepolo 11, I-34143 Trieste, Italy.;INAF, Osserv Astron Trieste, Via GB Tiepolo 11, I-34143 Trieste, Italy.;Ist Nazl Fis Nucl, Sez Trieste, Via A Valerio 2, I-34127 Trieste, Italy..
    Spitoni, E.
    Univ Trieste, Dipartimento Fis, Sez Astron, Via GB Tiepolo 11, I-34143 Trieste, Italy.;INAF, Osserv Astron Trieste, Via GB Tiepolo 11, I-34143 Trieste, Italy..
    Schultheis, M.
    Univ Cote Azur, Lab Lagrange, Observ Cote Azur, CS 34229, F-06304 Nice, France..
    Hayden, M.
    Univ Cote Azur, Lab Lagrange, Observ Cote Azur, CS 34229, F-06304 Nice, France..
    Hill, V.
    Univ Cote Azur, Lab Lagrange, Observ Cote Azur, CS 34229, F-06304 Nice, France..
    Zoccali, M.
    Pontificia Univ Catolica Chile, Fac Fis, Inst Astrofis, Av Vicuna Mackenna 4860, Santiago, Chile.;Millennium Inst Astrophys, Av Vicuna Mackenna 4860, Santiago 7820436, Chile..
    Minniti, D.
    Millennium Inst Astrophys, Av Vicuna Mackenna 4860, Santiago 7820436, Chile.;Univ Andres Bello, Dept Ciencias Fis, 220 Republ, Santiago, Chile.;Vatican Observ, I-00120 Vatican City, Vatican..
    Gonzalez, O. A.
    European Southern Observ, Alonso Cordova 3107 Vitacura, Santiago, Chile.;Univ Edinburgh, Royal Observ, Inst Astron, Blackford Hill, Edinburgh EH9 3HJ, Midlothian, Scotland..
    Gilmore, G.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Randich, S.
    INAF, Osserv Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Feltzing, S.
    Lund Observ, Dept Astron & Theoret Phys, Box 43, S-22100 Lund, Sweden..
    Alfaro, E. J.
    Inst Astrofis Andalucia, CSIC, Apdo 3004, Granada 18080, Spain..
    Babusiaux, C.
    Univ Paris Diderot, CNRS, GEPI, Observ Paris, 5 Pl Jules Janssen, F-92190 Meudon, France..
    Bensby, T.
    Lund Observ, Dept Astron & Theoret Phys, Box 43, S-22100 Lund, Sweden..
    Bragaglia, A.
    INAF, Osserv Astron Bologna, Via Ranzani 1, I-40127 Bologna, Italy..
    Flaccomio, E.
    INAF, Osserv Astron Palermo, Piazza Parlamento 1, I-90134 Palermo, Italy..
    Koposov, S. E.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Pancino, E.
    INAF, Osserv Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy.;ASI Sci Data Ctr, Via Politec SNC, I-00133 Rome, Italy..
    Bayo, A.
    Univ Valparaiso, Inst Fis & Astron, Valparaiso, Chile..
    Carraro, G.
    European Southern Observ, Alonso Cordova 3107 Vitacura, Santiago, Chile..
    Casey, A. R.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Costado, M. T.
    Inst Astrofis Andalucia, CSIC, Apdo 3004, Granada 18080, Spain..
    Damiani, F.
    INAF, Osserv Astron Palermo, Piazza Parlamento 1, I-90134 Palermo, Italy..
    Donati, P.
    INAF, Osserv Astron Bologna, Via Ranzani 1, I-40127 Bologna, Italy..
    Franciosini, E.
    INAF, Osserv Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Hourihane, A.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Jofre, P.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England.;Univ Diego Portales, Fac Ingn, Nucl Astron, Av Ejercito 441, Santiago, Chile..
    Lardo, C.
    Liverpool John Moores Univ, Astrophys Res Inst, 146 Brownlow Hill, Liverpool L3 5RF, Merseyside, England..
    Lewis, J.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Lind, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Max Planck Inst Astron, Konigstuhl 17, D-69117 Heidelberg, Germany..
    Magrini, L.
    INAF, Osserv Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Morbidelli, L.
    INAF, Osserv Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Sacco, G. G.
    INAF, Osserv Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Worley, C. C.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Zaggia, S.
    Univ Padua, INAF, Vicolo Osserv 5, I-35122 Padua, Italy..
    The Gaia-ESO Survey: Exploring the complex nature and origins of the Galactic bulge populations2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 601, article id A140Article in journal (Refereed)
    Abstract [en]

    Context. As observational evidence steadily accumulates, the nature of the Galactic bulge has proven to be rather complex: the structural, kinematic, and chemical analyses often lead to contradictory conclusions. The nature of the metal-rich bulge-and especially of the metal-poor bulge and their relation with other Galactic components, still need to be firmly defined on the basis of statistically significant high-quality data samples. Aims. We used the fourth internal data release of the Gaia-ESO survey to characterize the bulge metallicity distribution function (MDF), magnesium abundance, spatial distribution, and correlation of these properties with kinematics. Moreover, the homogeneous sampling of the different Galactic populations provided by the Gaia-ESO survey allowed us to perform a comparison between the bulge, thin disk, and thick disk sequences in the [Mg /Fe] vs. [Fe/H] plane in order to constrain the extent of their eventual chemical similarities. Methods. We obtained spectroscopic data for similar to 2500 red clump stars in 11 bulge fields, sampling the area -10 degrees <= l <= + 8 degrees and -10 degrees <= b <= -4 degrees from the fourth internal data release of the Gaia-ESO survey. A sample of similar to 6300 disk stars was also selected for comparison. Spectrophotometric distances computed via isochrone fitting allowed us to define a sample of stars likely located in the bulge region. Results. From a Gaussian mixture models (GMM) analysis, the bulge MDF is confirmed to be bimodal across the whole sampled area. The relative ratio between the two modes of the MDF changes as a function of b, with metal-poor stars dominating at high latitudes. The metal-rich stars exhibit bar-like kinematics and display a bimodality in their magnitude distribution, a feature which is tightly associated with the X-shape bulge. They overlap with the metal-rich end of the thin disk sequence in the [Mg/Fe] vs. [Fe/H] plane. On the other hand, metal-poor bulge stars have a more isotropic hot kinematics and do not participate in the X-shape bulge. Their Mg enhancement level and general shape in the [Mg/Fe] vs. [Fe/H] plane is comparable to that of the thick disk sequence. The position at which [Mg/Fe] starts to decrease with [Fe/H], called the "knee", is observed in the metal-poor bulge at [Fe/H] knee = -0.37 +/- 0.09, being 0.06 dex higher than that of the thick disk. Although this difference is inside the error bars, it suggest a higher star formation rate (SFR) for the bulge than for the thick disk. We estimate an upper limit for this difference of Delta [Fe/H](knee) = 0 : 24 dex. Finally, we present a chemical evolution model that suitably fits the whole bulge sequence by assuming a fast (< 1 Gyr) intense burst of stellar formation that takes place at early epochs. Conclusions. We associate metal-rich stars with the bar boxy/peanut bulge formed as the product of secular evolution of the early thin disk. On the other hand, the metal-poor subpopulation might be the product of an early prompt dissipative collapse dominated by massive stars. Nevertheless, our results do not allow us to firmly rule out the possibility that these stars come from the secular evolution of the early thick disk. This is the first time that an analysis of the bulge MDF and alpha-abundances has been performed in a large area on the basis of a homogeneous, fully spectroscopic analysis of high-resolution, high S/N data.

  • 46.
    Rojas-Arriagada, A.
    et al.
    Univ Cote dAzur, Lab Lagrange, Observ Cote dAzur, CNRS,Bvd Observ, CS 34229, F-06304 Nice 4, France..
    Recio-Blanco, A.
    Univ Cote dAzur, Lab Lagrange, Observ Cote dAzur, CNRS,Bvd Observ, CS 34229, F-06304 Nice 4, France..
    de Laverny, P.
    Univ Cote dAzur, Lab Lagrange, Observ Cote dAzur, CNRS,Bvd Observ, CS 34229, F-06304 Nice 4, France..
    Schultheis, M.
    Univ Cote dAzur, Lab Lagrange, Observ Cote dAzur, CNRS,Bvd Observ, CS 34229, F-06304 Nice 4, France..
    Guiglion, G.
    Univ Cote dAzur, Lab Lagrange, Observ Cote dAzur, CNRS,Bvd Observ, CS 34229, F-06304 Nice 4, France..
    Mikolaitis, S.
    Vilnius Univ, Inst Theoret Phys & Astron, A Gostauto 12, LT-01108 Vilnius, Lithuania..
    Kordopatis, G.
    Leibniz Inst Astrophys Postdam AIP, Sternwarte 16, D-14482 Potsdam, Germany..
    Hill, V.
    Univ Cote dAzur, Lab Lagrange, Observ Cote dAzur, CNRS,Bvd Observ, CS 34229, F-06304 Nice 4, France..
    Gilmore, G.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Randich, S.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy..
    Alfaro, E. J.
    CSIC, Inst Astrofis Andalucia, Apdo 3004, E-18080 Granada, Spain..
    Bensby, T.
    Lund Observ, Dept Astron & Theoret Phys, Box 43, S-22100 Lund, Sweden..
    Koposov, S. E.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England.;Moscow MV Lomonosov State Univ, Sternberg Astron Inst, Moscow 119992, Russia..
    Costado, M. T.
    CSIC, Inst Astrofis Andalucia, Apdo 3004, E-18080 Granada, Spain..
    Franciosini, E.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy..
    Hourihane, A.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Jofre, P.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Lardo, C.
    Liverpool John Moores Univ, Astrophys Res Inst, 146 Brownlow Hill, Liverpool L3 5RF, Merseyside, England..
    Lewis, J.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Magrini, L.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy..
    Monaco, L.
    Univ Andres Bello, Dept Ciencias Fis, Republica 220, Santiago, Chile..
    Morbidelli, L.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy..
    Sacco, G. G.
    Osserv Astrofis Arcetri, INAF, Largo E Fermi 5, I-50125 Florence, Italy..
    Worley, C. C.
    Univ Cambridge, Inst Astron, Madingley Rd, Cambridge CB3 0HA, England..
    Zaggia, S.
    Padova Observ, INAF, Vicolo Osservatorio 5, Padua, Italy..
    Chiappini, C.
    Leibniz Inst Astrophys Postdam AIP, Sternwarte 16, D-14482 Potsdam, Germany..
    The Gaia-ESO Survey: Separating disk chemical substructures with cluster models. Evidence of a separate evolution in the metal-poor thin disk2016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 586, article id A39Article in journal (Refereed)
    Abstract [en]

    Context. Recent spectroscopic surveys have begun to explore the Galactic disk system on the basis of large data samples, with spatial distributions sampling regions well outside the solar neighborhood. In this way, they provide valuable information for testing spatial and temporal variations of disk structure kinematics and chemical evolution. Aims. The main purposes of this study are to demonstrate the usefulness of a rigorous mathematical approach to separate substructures of a stellar sample in the abundance-metallicity plane, and provide new evidence with which to characterize the nature of the metal-poor end of the thin disk sequence. Methods. We used a Gaussian mixture model algorithm to separate in the [Mg/Fe] vs. [Fe/H] plane a clean disk star subsample (essentially at R-GC < 10 kpc) from the Gaia-ESO survey (GES) internal data release 2 (iDR2). We aim at decomposing it into data groups highlighting number density and/or slope variations in the abundance-metallicity plane. An independent sample of disk red clump stars from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) was used to cross-check the identified features. Results. We find that the sample is separated into five groups associated with major Galactic components; the metal-rich end of the halo, the thick disk, and three subgroups for the thin disk sequence. This is confirmed with the sample of red clump stars from APOGEE. The three thin disk groups served to explore this sequence in more detail. The two metal-intermediate and metal-rich groups of the thin disk decomposition ([Fe/H] > 0 : 25 dex) highlight a change in the slope at solar metallicity. This holds true at different radial regions of the Milky Way. The distribution of Galactocentric radial distances of the metal-poor part of the thin disk ([Fe/H] < 0 : 25 dex) is shifted to larger distances than those of the more metal-rich parts. Moreover, the metal-poor part of the thin disk presents indications of a scale height intermediate between those of the thick and the rest of the thin disk, and it displays higher azimuthal velocities than the latter. These stars might have formed and evolved in parallel and/or dissociated from the inside-out formation taking place in the internal thin disk. Their enhancement levels might be due to their origin from gas pre-enriched by outflows from the thick disk or the inner halo. The smooth trends of their properties (their spatial distribution with respect to the plane, in particular) with [Fe/H] and [Mg/Fe] suggested by the data indicates a quiet dynamical evolution, with no relevant merger events.

  • 47. Ruchti, G. R.
    et al.
    Read, J. I.
    Feltzing, S.
    Serenelli, A. M.
    McMillan, P.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Bensby, T.
    Bergemann, M.
    Asplund, M.
    Vallenari, A.
    Flaccomio, E.
    Pancino, E.
    Korn, Andreas J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Recio-Blanco, A.
    Bayo, A.
    Carraro, G.
    Costado, M. T.
    Damiani, F.
    Heiter, Ulrike
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
    Hourihane, A.
    Jofre, P.
    Kordopatis, G.
    Lardo, C.
    de Laverny, P.
    Monaco, L.
    Morbidelli, L.
    Sbordone, L.
    Worley, C. C.
    Zaggia, S.
    The Gaia-ESO Survey: a quiescent Milky Way with no significant dark/stellar accreted disc2015In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 450, no 3, p. 2874-2887Article in journal (Refereed)
    Abstract [en]

    According to our current cosmological model, galaxies like the Milky Way are expected to experience many mergers over their lifetimes. The most massive of the merging galaxies will be dragged towards the disc plane, depositing stars and dark matter into an accreted disc structure. In this work, we utilize the chemodynamical template developed in Ruchti et al. to hunt for accreted stars. We apply the template to a sample of 4675 stars in the third internal data release from the Gaia-ESO Spectroscopic Survey. We find a significant component of accreted halo stars, but find no evidence of an accreted disc component. This suggests that the Milky Way has had a rather quiescent merger history since its disc formed some 8-10 billion years ago and therefore possesses no significant dark matter disc.

  • 48. Scott, Pat
    et al.
    Grevesse, Nicolas
    Asplund, Martin
    Sauval, A. Jacques
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Takeda, Yoichi
    Collet, Remo
    Trampedach, Regner
    Hayek, Wolfgang
    The elemental composition of the Sun: I. The intermediate mass elements Na to Ca2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 573, article id A25Article in journal (Refereed)
    Abstract [en]

    The chemical composition of the Sun is an essential piece of reference data for astronomy, cosmology, astroparticle, space and geo-physics: elemental abundances of essentially all astronomical objects are referenced to the solar composition, and basically every process involving the Sun depends on its composition. This article, dealing with the intermediate-mass elements Na to Ca, is the first in a series describing the comprehensive re-determination of the solar composition. In this series we severely scrutinise all ingredients of the analysis across all elements, to obtain the most accurate, homogeneous and reliable results possible. We employ a highly realistic 3D hydrodynamic model of the solar photosphere, which has successfully passed an arsenal of observational diagnostics. For comparison, and to quantify remaining systematic errors, we repeat the analysis using three different 1D hydrostatic model atmospheres (MARCS, MISS and Holweger & Muller 1974, Sol. Phys., 39, 19) and a horizontally and temporally-averaged version of the 3D model (? 3D ?). We account for departures from local thermodynamic equilibrium (LTE) wherever possible. We have scoured the literature for the best possible input data, carefully assessing transition probabilities, hyperfine splitting, partition functions and other data for inclusion in the analysis. We have put the lines we use through a very stringent quality check in terms of their observed profiles and atomic data, and discarded all that we suspect to be blended. Our final recommended 3D+NLTE abundances are: log epsilon(Na) = 6.21 +/- 0.04, log epsilon(Mg) = 7.59 +/- 0.04, log epsilon(Al) = 6.43 +/- 0.04, log epsilon(Si) = 7.51 +/- 0.03, log epsilon(P) = 5.41 +/- 0.03, log epsilon(S) = 7.13 +/- 0.03, log epsilon(K) = 5.04 +/- 0.05 and log epsilon(Ca) = 6.32 +/- 0.03. The uncertainties include both statistical and systematic errors. Our results are systematically smaller than most previous ones with the 1D semi-empirical Holweger & Muller model, whereas the < 3D > model returns abundances very similar to the full 3D calculations. This analysis provides a complete description and a slight update of the results presented in Asplund et al. (2009, ARA&A, 47, 481) for Na to Ca, and includes full details of all lines and input data used.

  • 49.
    Sharma, Sanjib
    et al.
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia;ARC Ctr Excellence All Sky Astrophys Three Dimens, Canberra, ACT 2611, Australia.
    Stello, Dennis
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia;ARC Ctr Excellence All Sky Astrophys Three Dimens, Canberra, ACT 2611, Australia;Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia;Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
    Bland-Hawthorn, Joss
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia;ARC Ctr Excellence All Sky Astrophys Three Dimens, Canberra, ACT 2611, Australia.
    Hayden, Michael R.
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia;ARC Ctr Excellence All Sky Astrophys Three Dimens, Canberra, ACT 2611, Australia.
    Zinn, Joel C.
    Ohio State Univ, Dept Astron, Columbus, OH 43210 USA.
    Kallinger, Thomas
    Univ Vienna, Inst Astrophys, Turkenschanzstr 17, A-1180 Vienna, Austria.
    Hon, Marc
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Asplund, Martin
    ARC Ctr Excellence All Sky Astrophys Three Dimens, Canberra, ACT 2611, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Buder, Sven
    Heidelberg Univ, Int Max Planck Res, Sch Astron & Cosm Phys, Heidelberg, Germany;MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    De Silva, Gayandhi M.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia.
    D'Orazi, Valentina
    INAF, Vicolo Osservatorio 5, I-35122 Padua, PD, Italy.
    Freeman, Ken
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Kos, Janez
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Lewis, Geraint F.
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Lin, Jane
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. MPIA, Koenigstuhl 17, D-69117 Heidelberg, Germany.
    Martell, Sarah
    ARC Ctr Excellence All Sky Astrophys Three Dimens, Canberra, ACT 2611, Australia;Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Simpson, Jeffrey D.
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Wittenmyer, Rob A.
    Univ Southern Queensland, Ctr Astrophys, Toowoomba, Qld 4350, Australia.
    Zucker, Daniel B.
    Macquarie Univ, Dept Phys & Astron, Sydney, NSW 2109, Australia;Macquarie Univ, Res Ctr Astron Astrophys & Astrophoton, Sydney, NSW 2109, Australia.
    Zwitter, Tomaz
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Bedding, Timothy R.
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Chen, Boquan
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Cotar, Klemen
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Esdaile, James
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Horner, Jonathan
    Univ Southern Queensland, Ctr Astrophys, Toowoomba, Qld 4350, Australia.
    Huber, Daniel
    Aarhus Univ, Dept Phys & Astron, Stellar Astrophys Ctr, Ny Munkegade 120, DK-8000 Aarhus C, Denmark;Univ Hawaii, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA;SETI Inst, 189 Bernardo Ave, Mountain View, CA 94043 USA.
    Kafle, Prajwal R.
    Univ Western Australia, ICRAR, 35 Stirling Highway, Crawley, WA 6009, Australia.
    Khanna, Shourya
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Li, Tanda
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney, NSW 2006, Australia.
    Ting, Yuan-Sen
    Inst Adv Study, Princeton, NJ 08540 USA;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA;Observ Carnegie Inst Washington, 813 Santa Barbara St, Pasadena, CA 91101 USA.
    Nataf, David M.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    Nordlander, Thomas
    ARC Ctr Excellence All Sky Astrophys Three Dimens, Canberra, ACT 2611, Australia;Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 2611, Australia.
    Saadon, Mohd Hafiz Mohd
    Univ New South Wales, Sch Phys, Sydney, NSW 2052, Australia.
    Traven, Gregor
    Univ Ljubljana, Fac Math & Phys, Jadranska 19, Ljubljana 1000, Slovenia.
    Wright, Duncan
    Univ Southern Queensland, Ctr Astrophys, Toowoomba, Qld 4350, Australia.
    Wyse, Rosemary F. G.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
    The K2-HERMES Survey: age and metallicity of the thick disc2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 490, no 4, p. 5335-5352Article in journal (Refereed)
    Abstract [en]

    Asteroseismology is a promising tool to study Galactic structure and evolution because it can probe the ages of stars. Earlier attempts comparing seismic data from the Kepler satellite with predictions from Galaxy models found that the models predicted more low-mass stars compared to the observed distribution of masses. It was unclear if the mismatch was due to inaccuracies in the Galactic models, or the unknown aspects of the selection function of the stars. Using new data from the K2 mission, which has a well-defined selection function, we find that an oldmetal-poor thick disc, as used in previous Galactic models, is incompatible with the asteroseismic information. We use an importance-sampling framework, which takes the selection function into account, to fit for the metallicities of a population synthesis model using spectroscopic data. We show that spectroscopic measurements of [Fe/H] and [alpha/Fe] elemental abundances from the GALAH survey indicate a mean metallicity of log (Z/Z(circle dot)) = -0.16 for the thick disc. Here Z is the effective solar-scaled metallicity, which is a function of [Fe/H] and [alpha/Fe]. With the revised disc metallicities, for the first time, the theoretically predicted distribution of seismic masses show excellent agreement with the observed distribution of masses. This indirectly verifies that the asteroseismic mass scaling relation is good to within five per cent. Assuming the asteroseismic scaling relations are correct, we estimate the mean age of the thick disc to be about 10 Gyr, in agreement with the traditional idea of an old alpha-enhanced thick disc.

  • 50.
    Sharma, Sanjib
    et al.
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney.
    Stello, Dennis
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney; Univ New South Wales, Sch Phys, Sydney; Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Aarhus C.
    Buder, Sven
    MPIA, Heidelberg; Heidelberg Univ, Int Max Planck Res Sch Astron & Cosm Phys, Heidelberg.
    Kos, Janez
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney.
    Bland-Hawthorn, Joss
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney.
    Asplund, Martin
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston.
    Duong, Ly
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston.
    Lin, Jane
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston.
    Lind, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy. MPIA, Heidelberg.
    Ness, Melissa
    MPIA, Heidelberg.
    Huber, Daniel
    Univ Hawaii, Inst Astron, Honolulu; Univ Sydney, Sch Phys, Sydney Inst Astron SIfA, Sydney; SETI Inst, Mountain View; Aarhus Univ, Stellar Astrophys Ctr, Dept Phys & Astron, Aarhus C.
    Zwitter, Tomaz
    Univ Ljubljana, Fac Math & Phys, Ljubljana.
    Traven, Gregor
    Univ Ljubljana, Fac Math & Phys, Ljubljana.
    Hon, Marc
    Univ New South Wales, Sch Phys, Sydney.
    Kafle, Prajwal R.
    Univ Western Australia, ICRAR, Crawley.
    Khanna, Shourya
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney.
    Saddon, Hafiz
    Univ New South Wales, Sch Phys, Sydney.
    Anguiano, Borja
    Univ Virginia, Dept Astron, Charlottesville; Macquarie Univ, Dept Phys & Astron, Sydney.
    Casey, Andrew R.
    Monash Univ, Sch Phys & Astron, Clayton; Monash Univ, Fac Informat Technol, Clayton.
    Freeman, Ken
    Australian Natl Univ, Res Sch Astron & Astrophys, Weston.
    Martell, Sarah
    Univ New South Wales, Sch Phys, Sydney.
    De Silva, Gayandhi M.
    Univ Sydney, Sch Phys, Sydney Inst Astron, Sydney; Australian Astron Observ, N Ryde.
    Simpson, Jeffrey D.
    Univ Southern Queensland, Computat Engn & Sci Res Ctr, Toowoomba.
    Wittenmyer, Rob A.
    Univ Southern Queensland, Computat Engn & Sci Res Ctr, Toowoomba.
    Zucker, Daniel B.
    Macquarie Univ, Dept Phys & Astron, Sydney; Australian Astron Observ, N Ryde; Macquarie Univ, Res Ctr Astron Astrophys & Astrophoton, Sydney.
    The TESS-HERMES survey data release 1: high-resolution spectroscopy of the TESS southern continuous viewing zone2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 2, p. 2004-2019Article in journal (Refereed)
    Abstract [en]

    The Transiting Exoplanet Survey Satellite (TESS) will provide high-precision time series photometry for millions of stars with at least a half-hour cadence. Of particular interest are the circular regions of 12° radius centred around the ecliptic poles that will be observed continuously for a full year. Spectroscopic stellar parameters are desirable to characterize and select suitable targets for TESS, whether they are focused on exploring exoplanets, stellar astrophysics or Galactic archaeology. Here, we present spectroscopic stellar parameters (Teff, log g, [Fe/H], v sin i, vmicro) for about 16 000 dwarf and subgiant stars in TESS’ southern continuous viewing zone. For almost all the stars, we also present Bayesian estimates of stellar properties including distance, extinction, mass, radius and age using theoretical isochrones. Stellar surface gravity and radius are made available for an additional set of roughly 8500 red giants. All our target stars are in the range 10 < V < 13.1. Among them, we identify and list 227 stars belonging to the Large Magellanic Cloud. The data were taken using the High Efficiency and Resolution Multi-Element Spectrograph (HERMES; R ∼ 28 000) at the Anglo–Australian Telescope as part of the TESS–HERMES survey. Comparing our results with the TESS Input Catalogue (TIC) shows that the TIC is generally efficient in separating dwarfs and giants, but it has flagged more than 100 cool dwarfs (Teff < 4800 K) as giants, which ought to be high-priority targets for the exoplanet search. The catalogue can be accessed via http://www.physics.usyd.edu.au/tess-hermes/, or at Mikulski Archive for Space Telescopes (MAST).

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