Prospects for the formation of GW231123 from the AGN channel

TL;DR

This paper investigates the formation of the GW231123 black hole merger within active galactic nuclei, analyzing how initial mass functions influence the likelihood of such events and their consistency with observed data.

Contribution

It demonstrates that GW231123 can originate from the AGN channel and explores the impact of different black hole initial mass functions on merger properties.

Findings

GW231123 is consistent with a dynamical merger in an AGN environment.

Masses and spins suggest a merger of third and fourth generation black holes.

The likelihood analysis supports the AGN channel as a plausible formation scenario.

Abstract

The recent binary black hole (BBH) merger GW231123 consisted of the merger of two intermediate mass black holes (IMBH) which appear to have large spin magnitudes. Active galactic nuclei (AGN) are very promising environments for IMBH mergers and growth due to high escape velocities. Here we demonstrate how GW231123 can be produced in the AGN channel. Using the McFACTS code, we explore the impact of various choices of the black hole (BH) initial mass function (IMF) on predicted mass and spin magnitudes of BBH mergers from the AGN dynamical formation channel. By integrating the likelihood function for GW231123 with the detectable BBH population predicted from AGN using McFACTS, we demonstrate that GW231123 is consistent with a dynamical BBH merger from the AGN channel. We also postulate that the masses and spin magnitudes of GW231123 are most consistent with a merger of fourth and third generation BHs, for most choices of a segregated BH IMF and AGN lifetime.