The Origins of Off-Centre Massive Black Holes in Dwarf Galaxies
  Massive black holes often exist within dwarf galaxies, and both simulations
and observations have shown that a substantial fraction of these may be
off-center with respect to their hosts. We trace the evolution of off-center
massive black holes (MBHs) in dwarf galaxies using cosmological hydrodynamical
simulations, and show that the reason for off-center locations is mainly due to
galaxy-galaxy mergers. We calculate dynamical timescales and show that
off-center MBHs are unlikely to sink to their galaxys' centers within a Hubble
time, due to the shape of the hosts' potential wells and low stellar densities.
These wandering MBHs are unlikely to be detected electromagnetically, nor is
there a measurable dynamical effect on the galaxy's stellar population. We
conclude that off-center MBHs may be common in dwarfs, especially if the mass
of the MBH is small or the stellar mass of the host galaxy is large. However
detecting them is extremely challenging, because their accretion luminosities
are very low and they do not measurably alter the dynamics of their host
galaxies.
