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The GALAH survey and Gaia DR2: dissecting the stellar disc's phase space by age, action, chemistry, and location
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.
Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia.
Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia;Ctr Excellence Astrophys Three Dimens ASTRO 3D, Hawthorn, Vic, Australia.
Clarendon Lab, Rudolf Peierls Ctr Theoret Phys, Oxford OX1 3PU, England.ORCID iD: 0000-0002-1926-2436
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2019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 486, no 1, p. 1167-1191Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
OXFORD UNIV PRESS , 2019. Vol. 486, no 1, p. 1167-1191
Keywords [en]
astrometry, proper motions, stars: kinematics and dynamics, Galaxy: disc, evolution, structure
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-390635DOI: 10.1093/mnras/stz217ISI: 000474894100088OAI: oai:DiVA.org:uu-390635DiVA, id: diva2:1344697
Funder
Australian Research Council, DP150104667Australian Research Council, DP160103747Australian Research Council, DE140100598Swedish Research Council, 2015-00415_3Available from: 2019-08-21 Created: 2019-08-21 Last updated: 2019-08-21Bibliographically approved

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Lind, Karin

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