Intermediate-Mass Black Hole Feedback in Dwarf Galaxies: a View from Cosmological Simulations

Abstract

Black holes are usually observed to be of stellar-mass or supermassive. By natural extension, there should be a population of Intermediate-Mass Black Holes (IMBHs: with mass between $100$ to $10^6 M_{\odot}$) in the Universe; which has started to been observed. An exciting claim has been made recently by Silk (2017): that early feedback by IMBHs in gas-rich dwarf galaxies at $z=5-8$, can potentially solve multiple dwarf galaxy problems within the $\Lambda$-cold-dark-matter cosmology. We are performing Cosmological Hydrodynamical Simulations of $(2 Mpc)^3$ volumes, starting from $z=100$, to test the case for IMBHs in Dwarf Galaxies. Black holes of mass $1000 M_{\odot}$ are seeded inside halos when they reach a mass of $10^7 M_{\odot}$. The black holes grow by accretion of gas from their surroundings and by merger with other black holes, and consequently eject feedback energy. We analyze the simulation output in post-processing to study the growth of the first IMBHs, and their impact on star-formation. Our conclusions, based on numerical simulation results, support the phenomenological ideas made by Silk (2017). IMBHs at the centers of dwarf galaxies can be a strong source of feedback to quench star-formation and generate outflows. At the same time, these IMBHs form the missing link between stellar-mass and supermassive BHs.