Exploring Damped Lyman-$\alpha$ System Host Galaxies using Gamma-ray Bursts

TL;DR

This study analyzes 45 gamma-ray burst-associated Damped Lyman-alpha systems across redshifts 2-6 to understand their star formation and metallicity, revealing diverse efficiencies and episodic enrichment patterns.

Contribution

It provides the largest sample of GRB-DLA counterparts to date, offering new insights into star formation efficiency and metallicity evolution in high-redshift galaxy hosts.

Findings

DLA host star formation rates are uncorrelated with redshift or HI column density.

DLA hosts show a wide range of star formation efficiencies, deviating from local and cosmological models.

Metal enrichment times indicate episodic star formation and feedback effects.

Abstract

We present a sample of 45 Damped Lyman-$\alpha$ system (DLA, \nhi\ $ \geq 2 \times 10^{20} {\rm cm}^{-2}$) counterparts (33 detections, 12 upper limits) which host gamma-ray bursts (GRB-DLAs) in order to investigate star-formation and metallicity within galaxies hosting DLAs. Our sample spans $z \sim 2-6$ and is nearly three times larger than any previously detected DLA counterparts survey based on quasar line-of-sight searches (QSO-DLAs). We report star formation rates (SFRs) from rest-frame UV photometry and SED modeling. We find that DLA counterpart SFRs are not correlated with either redshift or HI column density. Thanks to the combination of \hst\ and ground-based observations, we also investigate DLA host star-formation efficiency. Our GRB-DLA counterpart sample spans both higher efficiency and low efficiency star formation regions compared to the local Kennicutt-Schmidt relation, local star formation laws, and $z \sim 3$ cosmological simulations. We also compare the depletion times of our DLA hosts sample to other objects in the local Universe, our sample appears to deviate from the star formation efficiencies measured in local spiral and dwarf galaxies. Furthermore, we find similar efficiencies as local inner disks, SMC, and LBG outskirts. Finally, our enrichment time measurements show a spread of systems with under- and over-abundance of metals which may suggest that these systems had episodic star formation and a metal enrichment/depletion as a result of strong stellar feedback and/or metal inflow/outflow.