The formation of super star clusters: Clues from the molecular interstellar medium in nearby galaxies

Nearby galaxies allow us to study more extreme modes of star formation than are found in our own Milky Way, such as giant HIT regions and super star clusters. Clues to the triggering of these unusual regions of star formation may be found in the properties of the molecular gas out of which these clusters form. I review the optical HST and ground-based millimeter-wave data on the stellar and molecular gas content of 30 Doradus in the LMC, which is the closest example of a giant HII region. The region also contains the star cluster R136, which may be the closest example of a super star cluster. One of the striking facts about R136 is that it has managed to clear away or destroy all the molecular gas in its immediate vicinity in only 1-2 Myr. I then discuss new millimeter-wave observations of the molecular gas in the interacting system NGC 4038/NGC 4039 (the Antennae). I combine these data with HST and ISO data to present a picture of collision-triggered star formation in the Antennae. The extremely massive molecular gas complexes identified in these data are the most likely sites for the formation of the many super star clusters seen in the Antennae. One challenge for future work is understanding the formation of these molecular gas complexes and whether they can be destroyed by the super star clusters that form within them.