Davide Fiacconi - April 5, 2017

Modelling black hole spin evolution in hydrodynamical simulations

Most general astrophysical conditions require two quantities to characterise a
black hole: its mass and angular momentum (or spin). At zeroth order, a black
hole can "communicate" with the surroundings owing to its mass, pulling material
in an almost newtonian fashion when far enough. On the other hand, the spin
starts to reveal the intrinsically relativistic nature of black holes and it can
affect the evolution of matter in the black hole proximity, namely in the
accretion disc. Not only this changes the radiative efficiency, and therefore
the amount of energy released by accretion, but it is also a tracer of the black
hole growth history and sets the recoil velocity of merging black holes. I will
describe the recent attempts to introduce a sub-grid model for the mass
accretion onto the black hole and the spin evolution via the coupling with the
underlying accretion disc. I will show very preliminary results from simulations,
discussing also the difficulties in creating a general model.