Intracluster Short Gamma-Ray Bursts by Compact Binary Mergers

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.

6 pages, 1 figure, accepted to ApJ Letters; added discussion about evolution of galaxies and clusters

References in corpus (4)

• The Importance of Mergers for the Origin of Intracluster Stars in Cosmological Simulations of Galaxy Clusters
• The dark matter halos of massive, relaxed galaxy clusters observed with Chandra
• The Kinematics of Intracluster Planetary Nebulae and the On-Going Subcluster Merger in the Coma Cluster Core
• A Putative Early-Type Host Galaxy for GRB 060502B: Implications for the Progenitors of Short-Duration Hard-Spectrum Bursts