Abstract
By using AMR cosmological hydrodynamic N-body zoom-in simulations, we studied the mass transport processes onto galactic nuclei from high redshift up to z∼6. We were able to study the mass accretion process on scales from ∼50 kpc to ∼ few pc. We studied the BH growth at the galactic center in relation with the mass transport processes associated to both the Reynolds and the gravitational stress on the disc. We found that in simulations that include radiative cooling and SN feedback, the SMBH grows at the Eddington limit for some periods of time presenting <fEDD>≈0.5 throughout its evolution. The α parameter is dominated by the Reynolds term, αR, with αR»1. The gravitational part of the α parameter, αG, has an increasing trend toward the galactic center at higher redshifts, with values αG∼1 at radii &lesssim, few 101 pc contributing to the BH fueling. In terms of torques, we also found that gravity has an increasing contribution toward the galactic center at earlier epochs with a mixed contribution above ∼100 pc. This complementary work between pressure gradients and gravitational potential gradients allows an efficient mass transport on the disc with average mass accretion rates of the order ∼ few 1M⊙/yr. These level of SMBH accretion rates found in our cosmological simulations are needed in all models of SMBH growth that attempt to explain the formation of redshift 6-7 quasars.
