IAU Symposium Abstract S186-081P

CO Observations of Luminous Infrared Galaxies in a Merger Sequence

Yu Gao1,2 and Philip Solomon1
1 Astronomy Program, State Univ. of New York at Stony Brook $<psolomon@astro.sunysb.edu>
2 Dept. of Astronomy, Univ. of Illinois at Urbana-Champaign (current address) <gao@astro.uiuc.edu>

In order to determine the relationship between the infrared and molecular gas properties and the galaxy-galaxy interactions, we study luminous infrared galaxy mergers (LIGMs) in the intermediate merging process. We have conducted new CO observations of LIGMs and found a correlation between the CO luminosity and the projected separation of merger nuclei in a sample of >50 LIGMs, which suggests that the molecular content is decreasing as merging advances. The correlation is better established with a sample of approximately 40 LIGMs excluding ultraluminous ones, which resembles more to a volume-limited, statistically complete sample of LIGMs in the local universe. One possible interpretation is that the molecular gas content of LIGMs is being rapidly depleted due to the merger-induced starbursts when merging progresses to more advanced stage. As a follow-up study, high resolution CO imaging has been mapped in 10 LIGMs selected to represent a merger sequence. Detailed results are discussed in an oral contribution by Gao et al.