The maximum offsets of binary neutron star mergers from host galaxies

TL;DR

This paper derives an analytical estimate for the maximum offset distances of binary neutron star mergers from their host galaxies, considering galaxy escape velocities, and discusses implications for host identification and related phenomena.

Contribution

It introduces an analytical formula for maximum merger offsets based on galaxy escape velocities, supported by population synthesis models, aiding in host galaxy association.

Findings

Maximum offset approximately 300 kpc scaled by escape velocity

High escape velocity galaxies are less likely to produce large offsets

Potential correlations between offsets, system masses, and gamma-ray burst durations

Abstract

We analytically derive, and illustrate with a population synthesis model, the maximum offset of binary neutron star mergers ejected from their host galaxies. This approximate maximum offset is 300 kpc $\times\ (v_\mathrm{esc} / 500\ \mathrm{km}\ \mathrm{s}^{-1})^{-7}$, where $v_\mathrm{esc}$ is the escape velocity from the host galaxy. Massive hosts with high escape velocities are unlikely to yield very large offsets. This maximum offset should inform the host associations of mergers that are not coincident with galaxies. We also discuss potential correlations between offsets and system masses, and possibly the duration of the gamma-ray burst accompanying the merger.