Growth of A Massive Black Hole Via Tidal Disruption Accretion

TL;DR

This study investigates how tidal disruption accretion (TDA) influences the early growth of massive black holes, showing TDA can significantly accelerate initial growth stages compared to gas accretion alone.

Contribution

It introduces a new implementation of TDA in high-resolution simulations and demonstrates its impact on early black hole growth, highlighting the importance of multiple accretion channels.

Findings

TDA can boost early black hole growth by over an order of magnitude.

MBH growth from 10^3 to >10^6 solar masses within 200 Myrs.

Star formation near the MBH is suppressed during active TDA phases.

Abstract

Stars that are tidally disrupted by the massive black hole (MBH) may contribute significantly to the growth of the MBH, especially in dense nuclear star clusters (NSCs). Yet, this tidal disruption accretion (TDA) of stars onto the MBH has largely been overlooked compared to the gas accretion (GA) channel in most numerical experiments until now. In this work, we implement a black hole growth channel via TDA in the high-resolution adaptive mesh refinement code Enzo to investigate its influence on a MBH seed's early evolution. We find that a MBH seed grows rapidly from $10^3\,\mathrm{M}_\odot$ to $\gtrsim 10^6\,\mathrm{M}_\odot$ in 200\,Myrs in some of the tested simulations. Compared to a MBH seed that grows only via GA, TDA can enhance the MBH's growth rate by up to more than an order of magnitude. However, as predicted, TDA mainly helps the early growth of the MBH (from $10^{3-4}\,\mathrm{M}_\odot$ to $\lesssim10^{5}\,\mathrm{M}_\odot$) while the later evolution is generally dominated by GA. We also observe that the star formation near the MBH is suppressed when TDA is most active, sometimes with a visible cavity in gas (of size $\sim$ a few pc) created in the vicinity of the MBH. It is because the MBH may grow expeditiously with both GA and TDA, and the massive MBH could consume its neighboring gas faster than being replenished by gas inflows. Our study demonstrates the need to consider different channels of black hole accretion that may provide clues for the existence of supermassive black holes at high redshifts.