The Antennae — a ULIRG in the Making

摘要

We report about a search for pre-starburst phenomena in colliding galaxy pairs which would represent a newly identified phase in the evolution of starbursts. We find exceptional =9.66μm v=0-0 S(3) H2 line emission of the Antennae galaxies. It arises mainly from the disk overlap region between the two nuclei. The H2 line luminosity, normalized by the far-infrared luminosity which traces the already active starburst contribution, exceeds that known for other infrared luminous galaxies. This excess implies that most of the gas clouds are in a pre-starburst phase shocked by the initial disk collisions and that new starbursts will be created soon. Our data reveal that much of the gas in the Antennae galaxies is in the exceptional and long sought-after phase before the onset of new starbursts.