I am mainly studying the formation and evolution of close pairs and binaries of massive black holes. In particular I put my efforts on how fast these binaries shrink by the extraction of angular momentum from the background stars and gas, and how the shrinking timescale depends on the properties of the host galaxies.

Characterizing the shrinking timescale of binaries will ultimately allow us to set important constraints on the expected number of close binaries, massive black hole coalescence events and the evolution black holes in the universe.

If the galaxies involved in a merger contain sufficient gas, a massive gaseous disc with a mass of ten to hundred times the mass of the black holes will form in the central kiloparsec of the merger remnant. The black holes in these nuclear region will form a binary that will shrink mainly due to the gravitational torques produced by the gaseous disc. I studied the transport of angular momentum from the binary to the disc and how this transport can result in the formation of a gap in the disc. If a gap forms, the shrinking of the binary will be dramatically delayed, otherwise the binary evolution will continue until the extraction of angular momentum by emission of gravitational waves becomes efficient enough to drive the final coalescence.

Surface density of eight simulations. The white dashed line encloses the region within twice the binary separation. The figures from the top are simulations equal mass black holes. The bottom figures are simulations where one black hole weighs 1/10 of the other. The simulations on the right show the presence of a gap carved by the binary.

gapnogap
Surface density of eight simulations. The white circle encompasses twice the binary separation. The top row shows equal mass black hole binaries, the bottom row binaries with a mass ratio 1:10. The simulations on the right show the presence of a gap carved by the binary’s evolution.