Title:
Prospects for Photon Observations of Merging Supermassive Black Holes
Abstract:
In CDM cosmologies, present-day large galaxies are assembled by merging a great many
smaller galaxies. Any black holes present in the merging galaxies should find their
way into the merged galaxy, and if they are massive, ultimately approach each other
near its center of mass. The presence of supermassive black holes at the centers of
contemporary galaxies suggests that in the long-run the black holes merge as well.
When they do, they emit a very large amount of energy in gravitational waves. In
addition, as the black holes come close to one another and merge, one would expect
dynamical disturbance to interstellar gas leading to photon emission--but no
direct observational signature of this process has ever been seen. Part of the
problem is that there is great controversy about what kind of light should be
radiated,
so it is difficult to know what to search for. In this talk I will review recent work
on how nearby gas interacts with the black hole merger process, as well as predictions
of how much, and what sort, of light might emerge. I will also briefly discuss
efforts
so far to identify black hole mergers electromagnetically.