Mitchell Institute for Fundamental Physics & Astronomy
College Station, Texas 77843
Local galaxies can be broadly divided into star-forming and quiescent galaxies. The physical mechanism responsible for star formation quenching is one of the most debated open questions for understanding galaxy evolution. As the fuel of star formation, the cold gas content in galaxies will provide direct observational evidence of how quenching may happen. By analyzing the observational data from SDSS, ALFALFA, GASS, and COLD GASS surveys, we find that disk galaxies with star formation rate well below the main sequence surprisingly have the same large atomic hydrogen (HI) gas reservoir as that of star-forming galaxies, but their molecular gas content and star formation efficiency are significantly lower. Thus, the large amount of HI gas reservoir cannot convert to stars efficiently, which is the direct reason of the low star formation rate. To identity the underlying internal physical origin, we further find that the quenching of these massive disk galaxies is closely related to the buildup of bulge, bar induced activities and low-luminosity AGN feedback. Our statistical analyses lead to a self-consistent picture of how “mass quenching” operates. On the other hand, we show that the residual amount of HI gas is an ideal probe to differentiate the mass quenching channel and the environment quenching channel for satellite galaxies.