Journal Article

An indirect measurement of gas evolution in galaxies at 0.5 < <i>z</i> < 2.0

G. Popping, K. I. Caputi, R. S. Somerville and S. C. Trager

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 425, issue 3, pages 2386-2400
Published in print September 2012 | ISSN: 0035-8711
Published online September 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21702.x
An indirect measurement of gas evolution in galaxies at 0.5 < z < 2.0

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Abstract

One key piece of information missing from high-redshift galaxy surveys is the galaxies’ cold gas contents. We present a new method to indirectly determine cold gas surface densities and integrated gas masses from galaxy star formation rates and to separate the atomic and molecular gas components. Our predicted molecular and total gas surface densities and integrated masses are in very good agreement with direct measurements quoted in the literature for low- and high-z galaxies. We apply this method to predict the gas content for a sample of ∼57000 galaxies in the Cosmic Evolution Survey (COSMOS) field at 0.5 < z < 2.0, selected to have IAB < 24mag. This approach allows us to investigate in detail the redshift evolution of galaxy's cold and molecular gas content versus stellar mass and to provide fitting formulae for galaxy gas fractions. We find a clear trend between galaxy gas fraction, molecular gas fraction and stellar mass with redshift, suggesting that massive galaxies consume and/or expel their gas at higher redshift than less massive objects and have lower fractions of their gas in molecular form. The characteristic stellar mass separating gas- from stellar-dominated galaxies decreases with time. This indicates that massive galaxies reach a gas-poor state earlier than less massive objects. These trends can be considered to be another manifestation of downsizing in star formation activity.

Keywords: ISM: molecules; galaxies: evolution; galaxies: formation; galaxies: ISM

Journal Article.  10502 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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