High-$z$ SMBHs in Cosmological Models with Enhanced Power Spectra

TL;DR

This study investigates how non-standard matter power spectra with bumps or blue tilts influence the early growth and formation epochs of supermassive black holes in cosmological models, revealing significant effects at high redshifts.

Contribution

It introduces the impact of non-power-law spectra on SMBH evolution using N-body simulations and semi-analytic models, highlighting differences from the standard $ ext{Lambda}$CDM model.

Findings

Massive SMBHs at $z=5-6$ are similar across models.

Bumpy spectra can increase SMBH masses tenfold at higher redshifts.

SMBH nucleation begins at $z\,\sim 13$, earlier than in $ ext{Lambda}$CDM.

Abstract

We consider the impact of non-power-law spectra of matter perturbations with a bump or with a blue tilt at small scales on the evolution of supermassive black holes (SMBHs) located the innermost part of galaxies. We study SMBH's mass growth rate and the epochs of their birth in four cosmological models using N-body simulations of dark matter within the box of $(100$~Mpc$/h)^3$. The simulations were populated with SMBHs using TRINITY semi-analytic model. We found that the most massive SMBHs at the redshifts $z=5-6$ are similar in all considered cosmologies, including the standard $\Lambda$CDM model. At larger $z$ the bumpy spectra can provide a tenfold increase (relative to $\Lambda$CDM model) in the masses of individual black holes without requiring super-Eddington accretion or heavy seeds. The nucleation of SMBHs starts at $z\sim 13$, which is earlier than in the standard $\Lambda$CMD model.