Rapid Formation of Supermassive Black Hole Binaries in Galaxy Mergers with Gas

摘要

Supermassive black holes (SMBHs) are a ubiquitous component of the nuclei ofgalaxies. It is normally assumed that, following the merger of two massivegalaxies, a SMBH binary will form, shrink due to stellar or gas dynamicalprocesses and ultimately coalesce by emitting a burst of gravitational waves.However, so far it has not been possible to show how two SMBHs bind during agalaxy merger with gas due to the difficulty of modeling a wide range ofspatial scales. Here we report hydrodynamical simulations that track theformation of a SMBH binary down to scales of a few light years following thecollision between two spiral galaxies. A massive, turbulent nuclear gaseousdisk arises as a result of the galaxy merger. The black holes form an eccentricbinary in the disk in less than a million years as a result of thegravitational drag from the gas rather than from the stars.