# On stellar-mass black hole mergers in AGN disks detectable with LIGO

## TL;DR

This paper models black hole mergers in AGN disks, predicting merger rates, mass, and spin spectra, and discusses how LIGO observations can constrain these models despite large uncertainties.

## Contribution

It provides a comprehensive parameterization of black hole merger characteristics in AGN disks and explores how LIGO data can constrain these models.

## Key findings

- Merger rate estimates range from 10^{-4} to 10^{4} Gpc^{-3} yr^{-1}.
- Mass spectrum follows a broken power-law with a merger-induced harder component.
- Spin spectrum is multi-peaked with retrograde spins influenced by gas disk evolution.

## Abstract

Black hole mergers detectable with LIGO can occur in active galactic nucleus (AGN) disks. Here we parameterize the merger rates, the mass spectrum and the spin spectrum of black holes (BH) in AGN disks. The predicted merger rate spans $\sim 10^{-4}-10^{4} \rm{Gpc}^{-1} \rm{yr}^{-1}$, so upper limits from LIGO ($<212\rm{Gpc}^{-1}\rm{yr}^{-1}$) already constrain it. The predicted mass spectrum has the form of a broken power-law consisting of a pre-existing BH powerlaw mass spectrum and a harder powerlaw mass spectrum resulting from mergers. The predicted spin spectrum is multi-peaked with the evolution of retrograde spin BH in the gas disk playing a key role. We outline the large uncertainties in each of these LIGO observables for this channel and we discuss ways in which they can be constrained in the future.