Session 83 - Starbursts and Mergers.
Oral session, Thursday, June 13
Union Theater,

## [83.02] Merging Progress of Luminous Infrared Galaxies as Traced by CO Observations

Y. Gao (Univ. of Illinois)

Most luminous infrared (IR) galaxies (LIRGs, L_IR \ge 2 \times 10^11 L_ødot) are closely interacting/merging galaxies rich in molecular gas. In order to address the relationship between the galaxy-galaxy interactions and the IR and molecular gas properties, and to better understand the star formation and merging processes in LIRGs as well as the evolution of LIRGs, we study here those LIRGs in their early or intermediate merging stages with the projected separation of the double nuclei can well be measured. The molecular gas content of LIRG mergers is measured by the CO(1-0) observations. The molecular gas properties and the IR luminosity have been compared with the galaxy-galaxy interaction stages characterized by the projected separation of merging nuclei. The principal result is that we have found a correlation between the CO luminosity (the molecular gas mass) and the projected separation of merger nuclei in a sample of \sim 50 LIRG mergers, which suggest that the molecular gas content is decreasing as merging advances. One possible interpretation is that the molecular gas content of LIRG mergers is being rapidly depleted due to the merger-induced enhanced strong starbursts when merging progresses to advanced stage. We have conducted CO observations of nearby LIRG mergers to form a statistically complete volume-limited sample of LIRG mergers, and with this nearly complete nearby sample, the correlation between the L_CO and the nuclear separation is better determined which has the same correlation slope as the one determined from larger, heterogenous sample. These results might have important constraints on both the merger-induced star formation models and the evolutionary scenario of LIRGs.