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