The galactic offsets of short gamma-ray bursts

Author: Ross Church

Abstract: Recent years have seen a combination of dedicated gamma-ray space missions such as Swift and Fermi with intensive multi-wavelength ground-based follow-up. Following the localisation of short-duration gamma-ray bursts by Swift, we have begun to probe the environments and host galaxies of short bursts. This gives us important information about the nature of their progenitors. I will present an updated version of the results presented in Church et al. (2011) with a larger sample of bursts. I will discuss modelling of the spatial offsets of bursts from their host galaxies and show that, assuming that the bursts form from the field population, the largest uncertainty comes from the modelling of the host galaxies. I will show that the majority of bursts show offsets that are consistent with a field binary origin; however, a small subset are too large to be explained in this way. They most likely either form through dynamical processes in the cores of globular clusters, or are ejected from their host galaxies during major mergers in the galaxies histories.