Songlines from Direct Collapse Seed Black Holes: Effects of X-rays on Black Hole Growth and Stellar Populations

TL;DR

This study uses cosmological simulations to explore how X-ray feedback from direct collapse black hole seeds influences their growth and nearby stellar populations, highlighting the importance of local radiation fields and gas dynamics.

Contribution

It introduces detailed simulations of DCBH seed formation considering X-ray irradiation, star formation, and feedback effects, revealing their impact on black hole growth and star formation.

Findings

X-ray feedback induces metal-free star formation shortly after MBH formation.

MBH growth is limited by local gas thermodynamics and large-scale gas dynamics.

Radiative feedback from MBHs significantly affects star formation and initial black hole growth.

Abstract

In the last decade, the growth of supermassive black holes (SMBHs) has been intricately linked to galaxy formation and evolution and is a key ingredient in the assembly of galaxies. To investigate the origin of SMBHs, we perform cosmological simulations that target the direct collapse black hole (DCBH) seed formation scenario in the presence of two different strong Lyman-Werner (LW) background fields. These simulations include the X-ray irradiation from a central massive black hole (MBH), $\rm{H}_2$ self-shielding and stellar feedback from metal-free and metal-enriched stars. We find in both simulations that local X-ray feedback induces metal-free star formation $\sim 0.5$ Myr after the MBH forms. The MBH accretion rate reaches a maximum of $10^{-3}$ $M_{\odot}$ yr$^{-1}$ in both simulations. However, the duty cycle differs which is derived to be $6\%$ and $50\%$ for high and low LW cases, respectively. The MBH in the high LW case grows only $\sim 6\%$ in 100 Myr compared to $16\%$ in the low LW case. We find that the maximum accretion rate is determined by the local gas thermodynamics whereas the duty cycle is determined by the large scale gas dynamics and gas reservoir. We conclude that radiative feedback from the central MBH plays an important role in star formation in the nuclear regions and stifling initial MBH growth, relative to the typical Eddington rate argument, and that initial MBH growth might be affected by the local LW radiation field.