Black Hole Growth and Feedback in Isolated Romulus25 Dwarf Galaxies

TL;DR

This study uses cosmological simulations to explore how massive black holes influence the structural evolution and star formation activity of isolated dwarf galaxies, revealing that overmassive black holes can suppress star formation.

Contribution

It demonstrates the impact of overmassive black holes on dwarf galaxy evolution and feedback processes, highlighting differences in growth and star formation suppression.

Findings

Overmassive BHs grow via mergers and high accretion rates.

Overmassive BH hosts have lower star formation rates.

Black hole feedback can quench star formation in dwarf galaxies.

Abstract

We investigate the effects of massive black hole growth on the structural evolution of dwarf galaxies within the Romulus25 cosmological hydrodynamical simulation. We study a sample of 228 central, isolated dwarf galaxies with stellar masses $M_{star} < 10^{10} M_\odot$ and a central BH. We find that the local $M_{BH} - M_{star}$ relation exhibits a high degree of scatter below $M_{star} < 10^{10} M_\odot$, which we use to classify BHs as overmassive or undermassive relative to their host $M_{star}$. Overmassive BHs grow through a mixture of BH mergers and relatively high average accretion rates, while undermassive BHs grow slowly through accretion. We find that isolated dwarf galaxies that host overmassive BHs also follow different evolutionary tracks relative to their undermassive BH counterparts, building up their stars and dark matter earlier and experiencing star formation suppression starting around $z=2$. By $z=0.05$, overmassive BH hosts above $M_{star} > 10^{9} M_\odot$ are more likely to exhibit lower central stellar mass density, lower HI gas content, and lower star formation rates than their undermassive BH counterparts. Our results suggest that overmassive BHs in isolated galaxies above $M_{star} > 10^{9} M_\odot$ are capable of driving feedback, in many cases suppressing and even quenching star formation by late times.