Nearly all Massive Quiescent Disk Galaxies have a Surprisingly Large Atomic Gas Reservoir

TL;DR

Most massive quiescent disk galaxies in the nearby universe surprisingly contain large reservoirs of atomic hydrogen gas, challenging previous assumptions that they are gas-poor due to residing in hot haloes.

Contribution

This study reveals that massive quiescent disk galaxies retain significant atomic gas, providing new insights into the star-formation quenching process in massive galaxies.

Findings

Massive quiescent disk galaxies have large atomic hydrogen reservoirs.

Both star-forming and quiescent disks show similar HI spectral profiles.

Quenched galaxies have reduced molecular gas and star formation efficiency.

Abstract

The massive galaxy population above the characteristic Schechter mass M*~10^10.6 Msun contributes to about half of the total stellar mass in the local Universe. These massive galaxies usually reside in hot dark matter haloes above the critical shock-heating mass ~10^12 Msun, where the external cold gas supply to these galaxies is expected to be suppressed. When galaxies run out of their cold gas reservoir, they become dead and quiescent. Therefore, massive quiescent galaxies living in hot haloes are commonly believed to be gas-poor. Based on the data from SDSS, ALFALFA, GASS and COLD GASS surveys, here we show that the vast majority of the massive, quiescent, central disk galaxies in the nearby Universe have a remarkably large amount of cold atomic hydrogen gas, surprisingly similar to star-forming galaxies. Both star-forming and quiescent disk galaxies show identical symmetric double-horn HI spectra, indicating similar regularly rotating HI disks. Relative to their star-forming counterparts, massive quiescent central disk galaxies are quenched because of their significantly reduced molecular gas content, lower dust content, and lower star formation efficiency. Our findings reveal a new picture, which clearly demonstrates the detailed star-formation quenching process in massive galaxies and provides a stringent constraint on the physical mechanism of quenching.