JCMT Mapping of CO(3-2) in the Circumnuclear Region of M31
  We present a survey of CO(3-2) molecular line emission in the circumnuclear
region of M31 with the James Clerk Maxwell Telescope (JCMT), aiming to explore
the physical conditions of the molecular gas. Significant CO(3-2) lines are
detected primarily along the so-called nuclear spiral, out to a projected
galactocentric radius of 700 pc at a linear resolution of ~50 pc. We find that
the velocity field of the molecular gas is in rough agreement with that of the
ionized gas previously determined from optical observations. Utilizing existed
CO(2-1) and CO(1-0) measurements in selected regions of the nuclear spiral, we
derive characteristic intensity ratios of CO(3-2)/CO(2-1) and CO(3-2)/CO(1-0),
which are both close to unity and are significantly higher than the typical
intensity ratios in the disk. Such line ratios suggest high kinetic
temperatures of the gas, which might be due to strong interstellar shocks
prevalent in the circumnuclear region.
