First IFU observations of two GRB host galaxies at cosmic noon with JWST/NIRSpec

TL;DR

This study presents the first JWST/NIRSpec IFU observations of two high-redshift GRB host galaxies, revealing complex, interacting galaxy environments and emphasizing the importance of spatially-resolved spectroscopy for understanding GRB progenitors.

Contribution

It provides novel spatially-resolved spectroscopic data of two GRB host galaxies at cosmic noon, demonstrating the complexity of their environments and the necessity of detailed observations.

Findings

Detected interacting galaxy environments with small spatial separation.

Measured gas-phase metallicities and SFRs consistent with other high-z star-forming galaxies.

Highlighted differences in properties of interacting galaxies, stressing the importance of spatial resolution.

Abstract

Long gamma-ray bursts (GRBs) serve as powerful probes of distant galaxies. Their luminous afterglow pinpoints galaxies independent of luminosity, in contrast to most flux-limited surveys. Nevertheless, GRB-selected galaxy samples are not free from bias, instead tracing the conditions favoured by the progenitor stars. Characterising the galaxy populations traced by GRBs is therefore important both to effectively use GRBs as probes as well as to place stronger constraints on the progenitor stars capable of forming long GRBs. Spatially-resolved spectroscopic observations with integral field units (IFUs) provide valuable insights into the interstellar medium and stellar populations of GRB host galaxies. In this paper we present results of the first two GRB host galaxies observed with the JWST/NIRSpec IFU with a spatial resolution of ~ 1.6 kpc; the hosts of GRB 150403A and GRB 050820A at redshifts z ~ 2.06 and z ~ 2.61, respectively. The data reveal two complex galaxy environments made up of two or more star forming galaxies that are likely interacting given their small spatial separation (< 20 kpc) and line of sight velocity offsets (< 100 km/s). The measured gas-phase metallicity, star formation rates (SFRs), and key diagnostic line ratios for each of the detected galaxies are overall consistent with the properties of other star forming galaxies and GRB hosts at z > 2. However, differences in the SFR and metallicities of the interacting galaxies highlight the importance of spatially resolved observations in order to accurately characterise the galaxy properties traced by GRBs.