ALMA Host galaxy observation of the off-axis Gamma-Ray Burst XRF020903

TL;DR

This study uses ALMA observations to analyze the host galaxy of XRF020903, supporting the idea that off-axis X-ray flashes and gamma-ray bursts share a common origin based on their similar radio properties.

Contribution

First detailed radio observation of an X-ray flash host galaxy, providing evidence for the off-axis GRB origin hypothesis.

Findings

Host galaxy's molecular gas properties match those of typical GRB hosts.

Gas depletion timescale is similar to GRB and super-luminous supernova hosts.

Radio properties support the off-axis GRB origin scenario.

Abstract

We investigated the radio properties of the host galaxy of X-ray flash, XRF020903, which is the best example for investigating of the off-axis origin of gamma-ray bursts(GRBs). Dust continuum at 233 GHz and CO are observed using the Atacama Large millimeter/submillimeter array. The molecular gas mass derived by applying the metalicity-dependent CO-to-H$_{2}$ conversion factor matches the global trend along the redshift and stellar mass of the GRB host galaxies. The estimated gas depletion timescale (pertaining to the potential critical characteristics of GRB host galaxies) is equivalent to those of GRBs and super-luminous supernova hosts in the same redshift range. These properties of the XRF020903 host galaxy observed in radio resemble those of GRB host galaxies, thereby supporting the identical origin of XRF020903 and GRBs.