Simulating the growth of Intermediate Mass Black Holes
  Theoretical models predict that a population of Intermediate Mass Black Holes
(IMBHs) of mass $M_\bullet \approx 10^{4-5} \, \mathrm{M_{\odot}}$ might form
at high ($z > 10$) redshift by different processes. Such objects would
represent the seeds out of which $z > 6$ Super-Massive Black Holes (SMBHs)
grow. We numerically investigate the radiation-hydrodynamic evolution governing
the growth of such seeds via accretion of primordial gas within their parent
dark matter halo of virial temperature $T_{vir} \sim 10^4 \, \mathrm{K}$. We
find that the accretion onto a Direct Collapse Black Hole (DCBH) of initial
mass $M_0=10^5 \, \mathrm{M_{\odot}}$ occurs at an average rate
$\dot{M}_{\bullet} \simeq 1.35 \, \dot{M}_{Edd} \simeq 0.1 \, \mathrm{M_{\odot}
\, yr^{-1}}$, is intermittent (duty-cycle $ < 50\%$) and lasts $\approx 142 \,
\mathrm{Myr}$; the system emits on average at super-Eddington luminosities,
progressively becoming more luminous as the density of the inner mass shells,
directly feeding the central object, increases. Finally, when $\approx 90\%$ of
the gas mass has been accreted (in spite of an average super-Eddington
emission) onto the black hole, whose final mass is $\sim 7 \times 10^6 \,
\mathrm{M_{\odot}}$, the remaining gas is ejected from the halo due to a
powerful radiation burst releasing a peak luminosity $L_{peak}\sim 3\times
10^{45} \, \mathrm{erg \, s^{-1}}$. The IMBH is Compton-thick during most of
the evolution, reaching a column density $N_H \sim 10^{25} \, \mathrm{cm^{-2}}$
in the late stages of the simulation. We briefly discuss the observational
implications of the model.
