Henize 2-10: the ongoing formation of a nuclear star cluster around a
  massive black hole
  The central region of the galaxy Henize 2-10 has a central black hole (BH)
with a mass of about $2\times 10^6$ M$_\odot$. While this black hole does not
appear to coincide with any central stellar over density, it is surrounded by
11 young massive clusters with masses above $10^5$ M$_\odot$. The availability
of high quality data on the structure of the galaxy and the age and mass of the
clusters provides excellent initial conditions for studying the dynamical
evolution of Henize 2-10's nucleus. Here we present a set of $N$-body
simulations of the central clusters and black hole to understand whether and
how they will merge to form a nuclear star cluster. Nuclear star clusters
(NSCs) are present in a majority of galaxies with stellar mass similar to
Henize 2-10. Despite the results depend on the choice of initial conditions, we
find that a NSC with mass $M_{NSC}\simeq 4-6\times 10^6$ M$_\odot$ and
effective radius $r_{NSC}\simeq 2.6-4.1$ pc will form within $0.2$ Gyr. This
work is the first showing, in a realistic realization of the host galaxy and
its star cluster system, that the formation of a bright nucleus is a process
that can happen after the formation of a central massive BH leading to a
composite NSC+BH central system. The merging process of the clusters does not
affect significantly the kinematics of the BH, whose motion, after the globular
cluster merger, is limited to a $\sim 1$ pc oscillation at less than $2$
kms$^{-1}$ speed.
