Wandering Black Holes in Bright Disk Galaxy Halos

Understand

We perform SPH+N-body cosmological simulations of massive disk galaxies, including a formalism for black hole seed formation and growth, and find that satellite galaxies containing supermassive black hole seeds are often stripped as they merge with the primary galaxy.

• These events naturally create a population of "wandering" black holes that are the remnants of stripped satellite cores; galaxies like the Milky Way may host 5 -- 15 of these objects within their halos.
• The satellites that harbor black hole seeds are comparable to Local Group dwarf galaxies such as the Small and Large Magellanic Clouds; these galaxies are promising candidates to host nearby intermediate mass black holes.
• Provided that these wandering black holes retain a gaseous accretion disk from their host dwarf galaxy, they give a physical explanation for the origin and observed properties of some recently discovered off-nuclear ultraluminous X-ray sources such as HLX-1.