Starbursts in Galaxies: Implications of Molecular and Far-infrared Observations

Starburst galaxies are defined in several ways (colors, optical spectroscopic signatures, and excess radio flux), and observational evidence indicating that episodes of rapid star formation occur in many galaxies with active nuclei is presented. There is a good correlation of 100 micron luminosity with CO emission, and of both quantities with excess nonthermal radio flux. This fact requires some linkage between central and global star formation rates. In addition, the presence of starbusts distorts the appearance of the molecular gas in which they occur. Using far infrared color temperatures and comparisons of CO isotopes, it is shown that the strong (12)CO emission in these galaxies does not accurately trace the H2 distribution, probably because the starburst raises the avearage temperature of the cloud ensemble.