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The SkyMapper DR1.1 search for extremely metal-poor stars
Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia.
Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia.
Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia;ARC Ctr Excellence Astrophys Three Dimens ASTRO 3, Canberra, ACT, Australia.
Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT 0200, Australia;ARC Ctr Excellence Astrophys Three Dimens ASTRO 3, Canberra, ACT, Australia.
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2019 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 489, no 4, p. 5900-5918Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
OXFORD UNIV PRESS , 2019. Vol. 489, no 4, p. 5900-5918
Keywords [en]
stars: abundances, stars: Population II, Galaxy: halo, Galaxy: stellar content
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-396696DOI: 10.1093/mnras/stz2550ISI: 000489302400103OAI: oai:DiVA.org:uu-396696DiVA, id: diva2:1368907
Funder
EU, Horizon 2020, 797100Available from: 2019-11-08 Created: 2019-11-08 Last updated: 2019-11-08Bibliographically approved

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Lind, Karin

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