Galaxies 09: Assembly, Gas Content and Star Formation History of Galaxies

Jarle Brinchmann
Leiden Observatory

Moving past the Kennicutt-Schmidt relation - gas-star formation scaling laws for 200,000 galaxies in the SDSS

The estimation of gas content in galaxies without radio/mm observations has long been dominated by the Kennicutt-Schmidt relationship which, while very useful, are merely scaling relationships and not measurements. Here we present a novel method of estimating total gas content from optical emission lines. We show that the technique gives very good results when compared to radio/mm estimates of gas content, with an accuracy comparable to that achieved in radio/mm studies. We then apply this to the SDSS DR7 and derive gas content distribution functions and the star-formation - gas content relation for ~200,000 galaxies spanning a wide range in physical properties. We study the $\mu_{gas} - \mu_{SFR}$ and gas mass/SFR vs stellar mass density relationships and show that both relationships depend on further parameters. We show in particular that the star formation efficiency, gas mass/SFR, is a clear function of metallicity. We end by pointing out the weaknesses and advantages of this technique for future studies, in particular the synergy with ALMA studies of galaxies.

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