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From K giants to G dwarfs: stellar lifetime effects on metallicity distributions derived from red giants

Citation

Manning, EM and Cole, AA, From K giants to G dwarfs: stellar lifetime effects on metallicity distributions derived from red giants, Monthly Notices of the Royal Astronomical Society, 471, (4) pp. 4194-4205. ISSN 0035-8711 (2017) [Refereed Article]


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DOI: doi:10.1093/mnras/stx1854

Abstract

We examine the biases inherent to chemical abundance distributions when targets are selected from the red giant branch (RGB), using simulated giant branches created from isochrones. We find that even when stars are chosen from the entire colour range of RGB stars and over a broad range of magnitudes, the relative numbers of stars of different ages and metallicities, integrated over all stellar types, are not accurately represented in the giant branch sample. The result is that metallicity distribution functions derived from RGB star samples require a correction before they can be fitted by chemical evolution models. We derive simple correction factors for over- and under-represented populations for the limiting cases of single-age populations with a broad range of metallicities and of continuous star formation at constant metallicity; an important general conclusion is that intermediate-age populations (≈14 Gyr) are over-represented in RGB samples. We apply our models to the case of the Large Magellanic Cloud bar and show that the observed metallicity distribution underestimates the true number of metal-poor stars by more than 25 per cent; as a result, the inferred importance of gas flows in chemical evolution models could potentially be overestimated. The age- and metallicity-dependences of RGB lifetimes require careful modelling if they are not to lead to spurious conclusions about the chemical enrichment history of galaxies.

Item Details

Item Type:Refereed Article
Keywords:stars: evolution, stars: low-mass, galaxies: evolution
Research Division:Physical Sciences
Research Group:Astronomical and Space Sciences
Research Field:Galactic Astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Physical Sciences
Author:Manning, EM (Miss Ellen Manning)
Author:Cole, AA (Associate Professor Andrew Cole)
ID Code:123473
Year Published:2017
Deposited By:Mathematics and Physics
Deposited On:2018-01-09
Last Modified:2018-01-10
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