Black hole, neutron star and white dwarf merger rates in AGN disks
  Advanced LIGO \& Advanced Virgo are detecting a large number of binary
stellar origin black hole (BH) mergers. A promising channel for accelerated BH
merger lies in active galactic nucleus (AGN) disks of gas around super-masssive
black holes. Here we investigate the relative number of compact object mergers
in AGN disk models, including BH, neutron stars (NS) and white dwarfs, via
Monte Carlo simulations. We find the number of all merger types in the bulk
disk grows $\propto t^{1/3}$ which is driven by the Hill sphere of the more
massive merger component. Median mass ratios of NS-BH mergers in AGN disks are
$\tilde{q}=0.07\pm 0.06(0.14\pm 0.07)$ for mass functions (MF) $M^{-1(-2)}$. If
a fraction $f_{AGN}$ of the observed rate of BH-BH mergers
(${\cal}{R}_{BH-BH}$) come from AGN, we expect a rate of NS-BH (NS-NS) mergers
from the AGN channel of ${\cal}{R}_{BH-NS} \sim f_{AGN}[10,300]\rm{Gpc}^{-3}
\rm{yr}^{-1}$,(${\cal}{R}_{NS-NS} \leq f_{AGN}400\rm{Gpc}^{-3} \rm{yr}^{-1}$).
Allowing for the ratio of NS-NS/BH-BH LIGO search volumes, from preliminary O3
results we can rule out the AGN channel as a dominant contribution to observed
NS-NS mergers. The number of lower mass gap events in this channel is a strong
function of the nuclear MF and mass segregation efficiency. Compact object
merger ratios derived from LIGO can restrict models of MF, mass segregation and
populations embedded in AGN disks. The expected number of EM counterparts to
NS-BH mergers in AGN disks at $z<1$ is $\sim
[30,900]{\rm{yr}}^{-1}(f_{AGN}/0.1)$. EM searches for flaring due to embedded
events in large AGN surveys will complement LIGO constraints on AGN models and
the embedded populations that must live in them.
