Three-dimensional radiation hydrodynamics simulations of wandering intermediate-mass black holes considering the anisotropic radiation and dust sublimation

Abstract

ABSTRACT By performing three-dimensional radiation hydrodynamics simulations, we study Bondi–Hoyle–Lyttleton accretion on to intermediate-mass black holes (BHs) wandering in the dusty gas. Here, we take into account the anisotropic radiation feedback and the sublimation of dust grains. Our simulations show that when the relative velocity between the BH and the gas is small ($\sim 20\rm\, km~s^{-1}$) and gas density is $\sim 10^4 \rm cm^{-3}$, the gas mainly accretes from near the equatorial plane of the accretion disc at a time-averaged rate of 0.6 per cent of the Bondi–Hoyle–Lyttleton rate. An ionized region like two spheres glued together at the equatorial plane is formed, and the dense shock shell appears near the ionization front. The BH is accelerated at $\sim 10^{-8}\, \rm cm~s^{-2}$ due to the gravity of the shell. For denser gas ($\sim 10^6 \rm cm^{-3}$), the time-averaged accretion rate is also 0.6 per cent of the Bondi–Hoyle–Lyttleton rate. However, the BH is decelerated at $\sim 10^{-7}\, \rm cm~s^{-2}$ due to gravity of the dense downstream gas although the dense shock shell appears upstream. Our simulations imply that intermediate-mass BHs in the early universe keep floating at $\gtrsim {\rm several}\, 10\, \rm km~s^{-1}$ without increasing mass in interstellar gas with density of $\sim 10^4\, \rm cm^{-3}$, and slow down and grow into supermassive BHs in galaxies with the density of $\sim 10^6\, \rm cm^{-3}$.