Properties of Molecular Gas in Galaxies in Early and Mid Stage of the
  Interaction: I. Distribution of Molecular Gas
  We present the results of 12CO(J = 1-0) mapping observations toward four
interacting galaxies in early and mid stages of the interaction to understand
the behavior of molecular gas in galaxy-galaxy interaction. The observations
were carried out using the 45-m telescope at Nobeyama Radio Observatory (NRO).
We compared our CO total flux to those previously obtained with single-dish
observations and found that there are no discrepancy between them. Applying a
typical CO-H2 conversion factor, all constituent galaxies have molecular gas
mass more than 10^9 M_sun. Comparisons to HI, Ks and tracers of SF such as
Halpha, FUV, 8 um and 24 um revealed that the distribution of molecular gas in
interacting galaxies in the early stage of the interaction differs from atomic
gas, stars and star-forming regions. These differences are not explained
without the result of the interaction. Central concentration of molecular gas
of interacting galaxies in the early stage of the interaction is lower than
that of isolated galaxies, which suggests molecular gas is distributed
off-centre and/or extends in the beginning of the interaction.
