Multiscale mass transport in z~6 galactic discs: fueling black holes

Abstract

By using AMR cosmological hydrodynamic N-body zoom-in simulations, with the RAMSES code, we studied the mass transport processes onto galactic nuclei from high redshift up to $z\sim 6$. Due to the large dynamical range of the simulations we were able to study the mass accretion process on scales from $\sim 50[kpc]$ to $\sim$ few $1[pc]$. We studied the BH growth on to the galactic center in relation with the mass transport processes associated to both the Reynolds stress and the gravitational stress on the disc. Such methodology allowed us to identify the main mass transport process as a function of the scales of the problem. We found that in simulations that include radiative cooling and SNe feedback, the SMBH grows at the Eddington limit for some periods of time presenting $⟨f_{EDD}⟩\approx 0.5$ throughout its evolution. The $\alpha$ parameter is dominated by the Reynolds term, ${\alpha }_R$, with ${\alpha }_R\gg 1$. The gravitational part of the $\alpha$ parameter, ${\alpha }_G$, has an increasing trend toward the galactic center at higher redshifts, with values ${\alpha }_G\sim 1$ at radii <$\sim$ few $10^1[pc]$ 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 $\sim 100[pc]$. 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 $\sim$ few $1[M_{\odot }/yr]$. 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.

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• The Assembly of the First Massive Black Holes
• Spatially Resolved [CII] Emission in SPT0346-52: A Hyper-Starburst Galaxy Merger at z~5.7
• Rapid growth of seed black holes during early bulge formation
• Intermediate-mass black holes from Population III remnants in the first galactic nuclei
• How AGN and SNe feedback affect mass transport and black hole growth in high redshift galaxies
• Global instability by runaway collisions in nuclear stellar clusters: Numerical tests of a route for massive black hole formation
• Super-Eddington growth of black holes in the early Universe: effects of disk radiation spectra
• Observational Support for Massive Black Hole Formation Driven by Runaway Stellar Collisions in Galactic Nuclei
• Cosmological simulations of quasar fueling to sub-parsec scales using Lagrangian hyper-refinement
• Efficiency of black hole formation via collisions in stellar systems: An analysis of data from simulations and observations
• Black hole fueling in galaxy mergers: A high-resolution analysis