Exhaustion of the gas next to M31's supermassive black hole
  New observations performed at IRAM Plateau de Bure reveal the absence of
molecular gas next to Andromeda's black hole. We derived a 3 sigma upper limit
on the molecular gas mass of 4300 Msol for the linewidth of 1000 km/s. This is
compatible with infra-red observations which reveal a hole in dust emission
next to the black hole. Some gas from stellar feedback is expected from the old
eccentric stellar disc population, but it is not accreted close to the black
hole. This absence of gas explains the absence of stellar formation observed in
this region contrary to what is observed next to Sgr A* in the Milky Way.
Either the gas has been swallowed by the black hole, or a feedback mechanism
has pushed the gas outside the central 1 pc. Nevertheless, we detect a small
clump of gas with a very small velocity dispersion at 2.4" from the black hole.
It is probable that this clumpy gas is seen in projection, as it does not
follow the rotation of the disk surrounding the black hole, its velocity
dispersion is ten times smaller than the expected velocity gradient and the
tidal shear from the black hole requires a gas density for this clump that is
not compatible with our observations.
