Not all peaks are created equal: the early growth of Supermassive Black Holes

TL;DR

This study uses constrained simulations to link the early growth of supermassive black holes to initial density peak features, revealing that compact, low tidal field peaks promote rapid black hole growth and compact host galaxies.

Contribution

It introduces a novel application of constrained Gaussian realizations to connect initial density peak characteristics with SMBH growth in cosmological simulations.

Findings

High compactness peaks lead to faster early SMBH growth.

Low tidal field regions foster more compact black hole host galaxies.

Initial peak shape influences the formation of dense gas clumps and black hole accretion.

Abstract

In this work, we use the constrained Gaussian realization technique to study the early growth of supermassive black holes (SMBHs) in cosmological hydrodynamic simulations, exploring its relationship with features of the initial density peaks on large scales, ~1 Mpc/h. Our constrained simulations of volume (20 Mpc/h)^3 successfully reconstruct the large-scale structure as well as the black hole growth for the hosts of the rare 10^9 Msun SMBHs found in the BlueTides simulation at z~7. We run a set of simulations with constrained initial conditions by imposing a 5 \sigma_0(R_G) peak on scale of R_G = 1 Mpc/h varying different peak features, such as the shape and compactness as well as the tidal field surrounding the peak. We find that initial density peaks with high compactness and low tidal field induce the most rapid BH growth at early epochs. This is because compact density peaks with a more spherical large scale matter distribution lead to the formation of high density gas clumps in the centers of halos, and thus boost early BH accretion. Moreover, such initially compact density peaks in low tidal field regions also lead to a more compact BH host galaxy morphology. This can explain the tight correlation between BH growth and host galaxy compactness seen in observations.