[Previous] | [Session 50] | [Next]
R.P. van der Marel (STScI)
Astronomers have long believed that black holes naturally form in the Universe in two mass ranges. Stellar-mass black holes form when a heavy star collapses under its own weight in a supernova explosion, and have been identified in X-ray binaries. Super-massive black holes probably form as a byproduct of galaxy formation, and are found in the centers of galaxies where they sometimes generate prodigious activity. However, black holes could have formed in the Universe in different mass ranges. Intermediate mass black holes of 102-105 solar masses are an especially interesting possibility, in particular since they may account for the intermediate luminosity X-ray objects that have recently been identified in nearby galaxies. I will review the possible formation mechanisms and observational constraints on such black holes, including the following issues: (a) formation through stellar evolution; (b) formation during galaxy formation; (c) primordial black hole formation; (d) constraints from microlensing; (e) intermediate mass black holes as dark halo constituents; and (f) intermediate mass black hole formation in stellar clusters.