Magnetic fields during the formation of supermassive black holes
  Observations of quasars at $\rm z> 6$ report the existence of a billion solar
mass black holes. Comprehending their formation in such a short time scale is a
matter of ongoing research. One of the most promising scenarios to assemble
supermassive black holes is a monolithic collapse of protogalactic gas clouds
in atomic cooling halos with $\rm T_{vir} \geq 10^{4} K$. In this article, we
study the amplification and impact of magnetic fields during the formation of
seed black holes in massive primordial halos. We perform high resolution
cosmological magnetohydrodynamics simulations for four distinct halos and
follow their collapse for a few free-fall times until the simulations reach a
peak density of $\rm 7 \times 10^{-10} g/cm^{3}$. Our findings show that
irrespective of the initial seed field, the magnetic field strength reaches a
saturated state in the presence of strong accretion shocks. Under such
conditions, the growth time becomes very short and amplification occurs rapidly
within a small fraction of the free-fall time. We find that the presence of
such strong magnetic fields provides additional support against gravity and
helps in suppressing fragmentation. Massive clumps of a few hundred solar
masses are formed at the end of our simulations and high accretion rates of
$\rm 1 M_{\odot}/yr$ are observed. We expect that in the presence of such
accretion rates, the clumps will grow to form supermassive stars of $\rm \sim
10^{5} M_{\odot}$. Overall, the role of the magnetic fields seems supportive
for the formation of massive black holes.
