Loss of star forming gas in SDSS galaxies

TL;DR

This study uses SDSS data and the Kennicutt law to analyze how gas loss in galaxies varies with stellar mass over cosmic time, supporting the galaxy downsizing model.

Contribution

It provides the first clear evidence of progressive gas loss in galaxies over cosmic epochs, especially in low-mass systems, using a novel combination of data and empirical relations.

Findings

Low-mass galaxies have lost nearly all cold baryons over time.

Massive galaxies have retained most of their gas and evolved faster.

Results support the downsizing scenario in galaxy evolution.

Abstract

Using the star formation rates from the SDSS galaxy sample, extracted using the MOPED algorithm, and the empirical Kennicutt law relating star formation rate to gas density, we calculate the time evolution of the gas fraction as a function of the present stellar mass. We show how the gas-to-stars ratio varies with stellar mass, finding good agreement with previous results for smaller samples at the present epoch. For the first time we show clear evidence for progressive gas loss with cosmic epoch, especially in low-mass systems. We find that galaxies with small stellar masses have lost almost all of their cold baryons over time, whereas the most massive galaxies have lost little. Our results also show that the most massive galaxies have evolved faster and turned most of their gas into stars at an early time, thus strongly supporting a downsizing scenario for galaxy evolution.