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Age derivation from UV absorption indices and the effect of the UV upturn

Published online by Cambridge University Press:  27 October 2016

Claire Le Cras ,
Claudia Maraston  and
Daniel Thomas
Claire Le Cras
Affiliation:
ICG, Uni. of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth, PO1 3FX email: [email protected], [email protected], [email protected]
Claudia Maraston
Affiliation:
ICG, Uni. of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth, PO1 3FX email: [email protected], [email protected], [email protected]
Daniel Thomas
Affiliation:
ICG, Uni. of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth, PO1 3FX email: [email protected], [email protected], [email protected]
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Abstract

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We exploit stellar population models of absorption features in the ultraviolet to assess their power in determining the age of the stellar population in galaxies. We focus in particular on features that can differentiate between an old UV-bright population, contributing to the UV upturn, and a young population due to recent star formation. We use a system of 8 indices between 2200 - 3200Å, tracing several chemical elements including Mg and Fe. We apply these models to a large sample of z ~ 0.6 massive galaxies from the Sloan Digital Sky Survey (SDSS) - III / Baryon Oscillation Spectroscopic Survey (BOSS) to derive the ages of the UV-bright populations. We find a subset of indices to be non-degenerate between old and young UV ages allowing us to find evidence for old stars contributing to the UV, rather than new star formation. We find up to 84% of our working sample (274,661 galaxies) to contain a contribution from old UV-bright stars. Those found to have higher contributing mass fractions being on average more massive and redder then those with lower mass fractions.

Keywords

galaxies: evolution - galaxies: stellar content - ultraviolet: galaxies
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , General Assembly A29B: Astronomy in Focus , August 2015 , pp. 190 - 192
Copyright
Copyright © International Astronomical Union 2016 

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