Intracluster Short Gamma-Ray Bursts by Compact Binary Mergers

TL;DR

This paper investigates how the escape of short gamma-ray bursts from galaxy clusters depends on dark matter distribution, proposing that intracluster SGRBs can reveal dark matter properties and their origin.

Contribution

It calculates the escape fraction of compact binaries in galaxy clusters and links it to dark matter distribution, offering a new observational test for SGRB origins.

Findings

Most SGRBs should escape and be hostless if dark matter is low.

Intracluster SGRB statistics can inform dark matter distribution.

High escape fraction correlates with stellar mass-dominated potentials.

Abstract

One of the possible origins of short gamma-ray bursts (SGRBs) is merging of compact binaries, and the effect of large kick velocity is a signature that can be used as an observational test for this hypothesis. Intracluster SGRBs that escaped from a host galaxy in a galaxy cluster are interesting in this context, since they would escape more easily by cluster tidal force, and would have brighter afterglow luminosity by dense intracluster gas, than those in general field galaxies. Here we calculate the escape fraction of compact binaries from their host galaxies in a galaxy cluster, and discuss some observational implications. We found that the escape fraction strongly depends on the nature of dark matter subhalos associated with member galaxies. If the amount of dark matter around member galaxies is not large and the gravitational potential for an escaping binary is determined mostly by stellar mass, most of SGRBs should escape and be observed as hostless, which is a much higher fraction than those in the field. Hence, statistics of intracluster SGRBs could give important information about the dark matter distribution in galaxy clusters, as well as hints for the origin of SGRBs.