http://arxiv.org/abs/2210.16319
Intermediate-Mass Black Holes (IMBHs), defined as having a mass in the range $10^3 \, \rm M_\odot$ to $10^6 \, \rm M_\odot$, are commonly found at the center of dwarf galaxies. Simulations and observations convincingly show that a sizable population of IMBHs could wander off-center in local galaxies. We use the cosmological simulation Astrid to study the orbital and radiative properties of wandering IMBHs in massive galaxies at $z \sim 3$. We find that this population of undetected black holes has large orbital inclinations ($60^\circ \pm 22^\circ$) with respect to the principal plane of the host. The eccentricity of their orbits is also significant ($0.6 \pm 0.2$) and decreases with time. Wandering IMBHs undergo spikes of accretion activity around the pericenter of their orbits, with rates $10^{-3}-10^{-5}$ times the Eddington rate and a median accretion duty cycle of $\sim 12 \%$. Their typical spectral energy distribution peaks in the infrared at $\sim 11 \, \mu \rm m$ rest frame. The studied IMBHs reach $2-10 \, \rm keV$ X-ray luminosities $> 10^{37} \, \mathrm{erg \, s^{-1}}$ for $\sim 10\%$ of the time. This luminosity corresponds to fluxes $>10^{-15} \, \mathrm{erg \, s^{-1} \, cm^{-2}}$ within $10$ Mpc. Two out of the 28 IMBHs studied ($\sim 7\%)$ have brief X-ray luminosity spikes $> 10^{41} \, \mathrm{erg \, s^{-1}}$, in the hyper-luminous X-ray sources (HLXs) regime. These findings suggest that HLXs are a small subset of the general wandering IMBH population, which is characterized by luminosities $10^3 – 10^4$ times fainter. Dedicated surveys with current and future observatories are needed to assess the demographics of this missing population of black holes.
E. Weller, F. Pacucci, Y. Ni, et. al.
Tue, 1 Nov 22
25/100
Comments: Submitted for publication in MNRAS. 8 pages, 7 figures
You must be logged in to post a comment.