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 _ { \sun } < M _ { tot } < 3 \times 10 ^ { 13 } M _ { \sun } 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 _ { \sun } , 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 .