IAU Symposium Abstract S186-069T

Luminous Infrared Galaxies in a Merging Sequence: BIMA CO Imaging

Yu Gao1, R. Gruendl1, C. Y. Hwang2 and K. Y. Lo1,2
1 Dept. of Astronomy, Univ. of Illinois, U.S.A. <gao, kyl, gruendl@astro.uiuc.edu>
2 Academia Sinica Institute of Astronomy and Astrophysics, Taiwan <hwang@biaa.sinica.edu.tw>

The correlation between the CO luminosity and the projected nuclear separation of interacting/merging galaxies suggests that the molecular gas content is decreasing as interaction advances (see poster contribution by Gao and Solomon), possibly a result of the gas depletion caused by the merger-induced starbursts. In order to provide observational constraints on the models of merger induced starbursts, we have been studying a sample of luminous infrared galaxies (LIGs) that may represent the various stages of the galaxy-galaxy merging process. Using the BIMA 9-element array, we have mapped the CO(1-0) emission from 10 LIGs, with special emphasis on early/intermediate stages of merging. An important finding is that some LIGs in the early merging or pre-merging stages could be in a \underbar{pre-starburst} phase. When combined with CO imaging data of advanced mergers in the literature, our results provide an interesting study of the evolution of the distribution and properties of the molecular gas along an entire merger sequence in a statistical sense. The systematic variations of the star formation properties along the merging sequence as revealed by ISO mid-infrared (see poster contribution by Hwang et al.) and VLA radio continuum imaging will also be briefly described and compared with the molecular gas properties.