What has quenched the massive spiral galaxies?
  Quenched massive spiral galaxies have attracted great attention recently, as
more data is available to constrain their environment and cold gas content.
However, the quenching mechanism is still uncertain, as it depends on the mass
range and baryon budget of the galaxy. In this letter, we report the
identification of a rare population of very massive, quenched spiral galaxies
with stellar mass $\gtrsim10^{11}{\rm~M_\odot}$ and halo mass
$\gtrsim10^{13}{\rm~M_\odot}$ from the Sloan Digital Sky Survey at redshift
$z\sim0.1$. Our CO observations using the IRAM-30m telescope show that these
galaxies contain only a small amount of molecular gas. Similar galaxies are
also seen in the state-of-the-art semi-analytical models and hydro-dynamical
simulations. It is found from these theoretical models that these quenched
spiral galaxies harbor massive black holes, suggesting that feedback from the
central black holes has quenched these spiral galaxies. This quenching
mechanism seems to challenge the popular scenario of the co-evolution between
massive black holes and massive bulges.
