The Galactic and Sub-Galactic Environments of Short-Duration Gamma-Ray Bursts: Implications for the Progenitors

TL;DR

This review summarizes recent discoveries about short gamma-ray burst environments, highlighting their diverse host galaxies, large offsets from galaxy centers, and implications for progenitor models like neutron star mergers.

Contribution

It provides a comprehensive synthesis of observational evidence linking short GRBs to neutron star mergers and other progenitors, emphasizing environmental differences from long GRBs.

Findings

Short GRBs occur in both elliptical and star-forming galaxies.

Offsets of short GRBs from galaxy centers are larger than for long GRBs.

Host galaxy environments suggest progenitors track stellar mass, consistent with neutron star mergers.

Abstract

The study of short-duration gamma-ray bursts (GRBs) has undergone a revolution in recent years thanks to the discovery of the first afterglows and host galaxies in May 2005. In this review we summarize our current knowledge of the galactic and sub-galactic environments of short GRBs, and the implications for the progenitor population. The most crucial results are: (i) some short GRBs occur in elliptical galaxies; (ii) the majority of short GRBs occur in star forming galaxies; (iii) the star forming hosts of short GRBs are distinct from the host galaxies of long GRBs in terms of star formation rates, luminosities, and metallicities, and instead appear to be drawn from the general field galaxy population; (iv) the physical offsets of short GRBs relative to their host galaxy centers are significantly larger than for long GRBs; (v) the observed offset distribution agrees well with predictions for the locations of NS-NS binary mergers; and (vi) unlike long GRBs, which tend to occur in the brightest regions of their hosts, the environments of short GRBs generally under-represent the light distribution of their host galaxies. Taken together, these observations suggest that short GRB progenitors have a wide age distribution and generally track stellar mass rather than star formation activity. These results are fully consistent with NS-NS binary mergers, but partial contribution from prompt or delayed magnetar formation is also consistent with the data.