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Unveiling the propertiesof molecular complexes in the Antennae
galaxies (NGC 4038/39) through CO (J=3-2) observations
内容
We present high-resolution CO (3-2) observations of the Antennae
galaxies obtained with the Submillimeter Array. The Antennae galaxies
(NGC 4038/39) are the face-on colliding galaxy pair at the
intermediate stage of the collision located at a distance of 22 Mpc.
The synthesized beam is ~ 1.3″, which corresponds to 140 pc at the
distance of the Antennae. This is the highest angular resolution
submillimeter image of the Antennae obtained to date. We detect using
the Clumpfind algorithm 57 molecular complexes, and 33 of them are
located in the overlap region between the two nuclei, which is the
active star forming region. Assuming a beam filling factor of unity,
the mean CO (3-2)/(1-0) brightness temperature ratios range between
0.3 and 0.8. On average the CO (3-2) line in the Antennae is
subthermally excited, however the ratios in the nucleus of NGC 4039
and the southern complexes in the overlap region are close to unity in
some localized regions. The cloud with the high ratio in the overlap
region coincide with the most active star forming region and thus the
high ratio is likely caused by star formation.
On the other hand, the nucleus of NGC 4039 has a relatively inactive
star forming region with no signs of an active AGN. We found two
molecular gas components that are kinematically distinct in NGC 4039,
and the boundary line of the two components corresponds to the region
with the highest CO (3-2)/(1-0) line ratio. In this region we suggest
that the molecular gas collisions produce the high line ratio.