Cold Molecular Gas Along the Merger Sequence in Local Luminous Infrared
  Galaxies
  We present an initial result from the 12CO (J=1-0) survey of 79 galaxies in
62 local luminous and ultra-luminous infrared galaxy (LIRG and ULIRG) systems
obtained using the 45 m telescope at the Nobeyama Radio Observatory. This is
the systematic 12CO (J=1-0) survey of the Great Observatories All-sky LIRGs
Survey (GOALS) sample. The molecular gas mass of the sample ranges 2.2 x 10^8 -
7.0 x 10^9 Msun within the central several kiloparsecs subtending 15" beam. A
method to estimate a size of a CO gas distribution is introduced, which is
combined with the total CO flux in the literature. The method is applied to a
part of our sample and we find that the median CO radius is 1-4 kpc. From the
early stage to the late stage of mergers, we find that the CO size decreases
while the median value of the molecular gas mass in the central several kpc
region is constant. Our results statistically support a scenario where
molecular gas inflows towards the central region from the outer disk, to
replenish gas consumed by starburst, and that such a process is common in
merging LIRGs.
