Simulating the dynamics of binary black holes in nuclear gaseous discs

We study the pairing of massive black holes embedded in a massive circum-nuclear, rotationally supported disc, until they form a close binary. Using high resolution SPH simulations, we follow the black hole dynamics, and in particular the eccentricity evolution, as a function of the composition in stars and gas of the disc. Binary-disc interaction always leads to orbital decay and, in case of co-rotating black holes, to orbit circularization. We present also a higher resolution simulation performed using the particle-splitting technique showing that the binary orbital decay is efficient down to a separation of ~ 0.1 pc, comparable to our new resolution limit. We detail the gaseous mass profile bound to each black hole. Double nuclear activity is expected to occur on an estimated timescale of ≲ 10 Myrs.