Where can we find the merger remnant in BH-BH mergers in Globular clusters?

TL;DR

This paper investigates the fate of black hole merger remnants in globular clusters, analyzing how recoil velocities influence whether remnants are retained, escape to the bulge, or become halo objects, using orbital data from GAIA EDR3.

Contribution

It provides a detailed analysis of the dynamical evolution of merger remnants in globular clusters considering recoil velocities and cluster properties, offering insights into their final locations.

Findings

Remnants with recoil velocity below 120 km/s tend to end up in the bulge.

Most black hole remnants are retained within the globular cluster if recoil velocity is low.

The study applies orbital data from GAIA EDR3 to real globular clusters.

Abstract

Mergers of black holes and other compact objects produce gravitational waves which carry a part of the energy, momentum, and angular momentum of the system. Due to asymmetry in the gravitational wave emission, a recoil kick velocity is imparted to the merger remnant. It has been conjectured that a significant fraction of the mergers detected so far reside in globular clusters. We explore the scenario where the merger remnant in a globular cluster is moving at a significant speed with respect to the binary that underwent merger. We study this in the situation when the kick velocity is higher than the escape velocity in the case of globular clusters assuming a Plummer density profile for the cluster. We study the evolution of the system to study the outcome: whether dynamical friction can trap the black hole within the globular cluster, whether the black hole escapes the globular cluster but ends up in the bulge, and lastly, whether the black halo becomes a halo object. We present results for an analysis based on orbital parameters of ten globular clusters using data from GAIA EDR3. We find that if the kick velocity is smaller than $120$ km/s then a majority of remnant black holes end up in the bulge. Note that our results in terms of where compact objects launched from a globular cluster end up are applicable to any mechanism, e.g., a compact object ejected due to three-body interactions.