IAU Symposium Abstract S186-082P

Luminous Infrared Galaxies in a Merging Sequence: ISO Observations

C.-Y. Hwang1, Y. Gao2, R. Gruendl2, and K. Y. Lo$^{1,2}$, N.-Y. Lu3
1 Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan < hwang@biaa.sinica.edu.tw >
2 Dept. of Astronomy, Univ. of Illinois, U.S.A.
< gao, kyl, gruendl@astro.uiuc.edu >
3 IPAC, Caltech, U.S.A. < lu@ipac.caltech.edu >

We report mid-infrared observations of several luminous infrared galaxies (LIGs) taken with the Infrared Space Observatory (ISO). We have been studying a sample of LIGs that were choosen to represent different phases of a merger sequence of galaxy-galaxy interaction with special emphasis on early/intermediate stages of merging. The goal is to do a synoptic study of the evolution of physical conditions in these LIGs along the merger sequence. We have observed these LIGs at several different wavebands: CO(1-0) emission, which traces the distribution and properties of the molecular gas, has been mapped at high spatial resolution using the Berkeley-Illinois-Maryland array (BIMA) (see contribution by Gao et al.). To determine observationally when enhanced star formation activity in these LIGs turn on along the merging sequence, we have also observed these LIGs at mid-infrared (15 and 7 micron) with the ISOCAM imaging facility on board the ISO satellite. The spatial resolution of these observations is about 6 arcsec, which is comparable with the BIMA C-configuration observations. We present here our first ISOCAM results of some of these LIGs and discuss possible implications of the observations.