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Stellar population gradients in GASS

Published online by Cambridge University Press:  17 July 2013

Jonas Johansson ,
Guinevere Kauffmann  and
Sean Moran
Jonas Johansson
Affiliation:
Max-Planck Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany
Guinevere Kauffmann
Affiliation:
Max-Planck Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany
Sean Moran
Affiliation:
Department of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
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Abstract

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We study relationships between the stellar populations and interstellar medium in massive galaxies using the Galex Arecibo SDSS Survey (GASS). The sample consists of HI-observations (~1000 galaxies) and complementary H2-observations (330 galaxies) and long-slit spectroscopy (230 galaxies). Luminosity-weighted stellar population ages, metallicitites and element abundance ratios, are derived by fitting stellar population models of absorption line indices. We find that the ages correlate more strongly with molecular gas fraction (MH2/M*) than with neutral Hydrogen fraction (MHI/M*). This result strengthens the theory that H2 is a better tracer of star-formation than HI. The sample is dominated by negative metallicity-gradients and flat Mg/Fe-gradients. Galaxies with high MH2/M*-ratios show in general flat or weakly negative age-gradients. For low MH2/M*-ratios the age-gradients are overall negative. These results are in agreement with the inside-out galaxy formation scenario. For galaxies with high r90/r50-ratios, a sub-population show positive age-gradients indicating additional formation channels. Furthermore, for galaxies with high MH2/M*-ratios more massive systems have older stellar populations in their centers, suggesting downsizing within the inside-out formation scenario.

Keywords

galaxies: evolution – galaxies: elliptical and lenticularcD – galaxies: spiral – galaxies: stellar content
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 8 , Symposium S295: The intriguing life of massive galaxies , August 2012 , pp. 304 - 307
Copyright
Copyright © International Astronomical Union 2013 

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