Host galaxies and relativistic ejecta of compact binary mergers in the ngVLA era

TL;DR

This paper explores how the next-generation Very Large Array (ngVLA) can advance multi-messenger astronomy by enabling detailed studies of host galaxies and relativistic ejecta from compact binary mergers, especially in the era of gravitational wave detections.

Contribution

It proposes that the ngVLA's enhanced sensitivity and resolution will allow detailed radio studies of merger hosts and ejecta, providing new insights into merger environments and dynamics.

Findings

ngVLA can identify host galaxies of GW mergers through EM counterparts or spatial distribution.

It enables resolved radio studies of star-forming regions and AGN in host galaxies.

Direct size measurements of relativistic ejecta will be possible, revealing their dynamics.

Abstract

We present the results of a community study aimed at exploring some of the scientific opportunities that the next generation Very Large Array (ngVLA) could open in the field of multi-messenger time-domain astronomy. We focus on compact binary mergers, golden astrophysical targets of ground-based gravitational wave (GW) detectors such as advanced LIGO. A decade from now, a large number of these mergers is likely to be discovered by a world-wide network of GW detectors. This will enable the identification of host galaxies, either directly through detection of electromagnetic (EM) counterparts, or indirectly by probing potential anisotropies in the spatial distribution of mergers. Identifying the host galaxy population of GW mergers would provide a way to constrain the efficiency of various binary neutron star (NS) or black hole (BH) formation scenarios, and the merger timescale distributions as linked to merger rates in early- and late-type galaxies. We discuss how a radio array with ~10x the sensitivity of the current Karl G. Jansky VLA and ~10x the resolution, would enable resolved radio continuum studies of binary merger hosts, probing regions of the galaxy undergoing star formation (which can be heavily obscured by dust and gas), AGN components, and mapping the offset distribution of the mergers with respect to the host galaxy light. For compact binary mergers containing at least one NS and with associated EM counterparts, we show how the ngVLA would enable direct size measurements of the relativistic merger ejecta and probe, for the first time directly, their dynamics.