Molecules in Starburst and Active Galaxy Nuclei
Molecular line surveys of luminous infrared bright galaxies sampled by the IRAS survey have shown these galaxies to be extraordinarily rich in molecular gas. Optical imaging of the most luminous IRAS galaxies suggest that many have recently undergone a strong galactic interaction or merger. High resolution aperture synthesis CO data in the systems reveal massive concentrations of molecules (10⁸ – 10¹⁰ M⊙) ususally in the galactic nuclei. The dense molecular gas is much more highly concentrated than in normal galaxies, probably a result of the viscous dissipation of energy and angular momentum in the ISM as a result of the strong dynamical perturbations. These nuclear gas concentrations are the source of nuclear starbursts, possibly also rejuvinating nuclear nonthermal activity. Interaction induced activity in the interstellar gas of galaxies may play a fundamental role in galactic evolution — leading to star formation rates elevated by at least an order of magnitude for a period ~ 2 × 10⁸ years. Since such activity is presently occurring in approximately 2% of all spiral galaxies, it is clear that galactic interactions can be critical to both the long term stellar populations of galaxies and to the most luminous, energetic phases for galactic evolution.
© 1994 Springer Science+Business Media Dordrecht. This research was supported in part by NSF grant AST 90-16404. It is a pleasure to thank Alicia Rodriguez for the preparation of this manuscript.