The Fates of Merging Supermassive Black Holes and a Proposal for a New
  Class of X-Ray Sources
  We perform N-body simulations on some of the most massive galaxies extracted
from a cosmological simulation of hierarchical structure formation with total
masses in the range $10^{12} M_{\odot} < M_{tot} < 3\times 10^{13} M_{\odot}$
from $4\geq z \geq 0$. After galactic mergers, we track the dynamical evolution
of the infalling black holes (BHs) around their host's central BHs. From 11
different simulations, we find that, of the 86 infalling BHs with masses >
$10^4 M_{\odot}$, 36 merge with their host's central BH, 13 are ejected from
their host galaxy, and 37 are still orbiting at $z=0$. Across all galaxies, 33
BHs are kicked to a higher orbit after close interactions with the central BH
binary or multiple, after which only one of them merged with their hosts. These
orbiting BHs should be detectable by their anomalous (not Low Mass X-ray
Binary) spectra. The X-ray luminosities of the orbiting massive BHs at z=0 are
in the range $10^{28}-10^{43}$ $\mathrm{erg}~\mathrm{s}^{-1}$, with a currently
undetectable median value of $10^{33}$ $\mathrm{erg}~\mathrm{s}^{-1}$. However,
the most luminous $\sim$5\% should be detectable by existing X-ray facilities.
