Abstract
In this article, we select 22 interacting galaxies for studying their physical difference and similarities. I organise this article as following parts. Part. I, I describe their optical, near-infrared, and CO(1-0) properties. Part. II, the main point is their properties of 20 cm radio continuum. Part. III, I discusse the typical interacting galaxies, the Antennae, of its kinematics of molecular clouds in interacting region. And, the descriptions of interacting galaxies are in Part. IV. Part. I. We have studied optical, near-infrared, and CO properties of the 22 luminous infrared galaxies in a merging sequence. We find no systematic variations of nuclear color, spectral type, equivalance of stellar absorption lines as a function of nuclear separation. However, we find a weak correlation of the line width and star formation rate as a function of nuclear separation. These results suggest that star formation activity initiates at any moment of tidal interaction with relatively short period of time and this activity can occur recursively since we find no systematic change of starburst age as a function of nuclear separation. Part. II. Star formation rate ($SFR$), especially in the nucleus region is enhanced by the merging process of two galaxies. The $SFR$ in interacting galaxies with massive bulge would be enhanced by 20-150 times compared to that in the isolated galaxies (Mihos \& Hernquist; 1994, 1996). In order to study $SFR$ in interacting galaxies, we have selected 22 galaxies based on the infrared luminosity. For these galaxies, we have observed CO(1-0) line emission with the $BIMA$ b, c array and 20 cm radio continuum with the $VLA$ telescope. We find that there's no clear trends that $SFR$ correlates with the projected nuclear separation. The $SFR$ correlates with the mass of molecular hydrogen but not with the dust temperature. Part. III. The non-starburst galaxy, the Antennae, is active in the overlap region of two disks. Previous work concluded that the active star formation activity is due to the collision of these two disks. The near-infrared line spectroscopy conflicts with this claim. We conclude that these two molecular clouds are leaving from each other rather than approaching to each other, therefore there must be other mechanisms for this active star formation activity.