High-redshift Damped Ly-alpha Absorbing Galaxy Model Reproducing the N(HI)-Z Distribution

TL;DR

This paper presents a model that reproduces the distribution of metallicity and HI column density in high-redshift DLAs, revealing their association with a broad range of star-forming galaxies and a metallicity gradient dependent on galaxy luminosity.

Contribution

The study introduces a physically motivated model that successfully reproduces the joint distribution of metallicity and HI column density in high-redshift DLAs, emphasizing the role of metallicity gradients.

Findings

DLAs trace galaxies across a wide luminosity range.

Most DLA cross-section arises in galaxies with ~0.1 L* at z~2.5.

The model favors a metallicity gradient scaling with galaxy luminosity.

Abstract

We investigate how damped Lyman-$\alpha$ absorbers (DLAs) at z ~ 2-3, detected in large optical spectroscopic surveys of quasars, trace the population of star-forming galaxies. Building on previous results, we construct a model based on observed and physically motivated scaling relations in order to reproduce the bivariate distributions of metallicity, Z, and HI column density, N(HI). Furthermore, the observed impact parameters for galaxies associated to DLAs are in agreement with the model predictions. The model strongly favours a metallicity gradient, which scales with the luminosity of the host galaxy, with a value of $\gamma$* = -0.019 $\pm$ 0.008 dex kpc$^{-1}$ for L* galaxies that gets steeper for fainter galaxies. We find that DLAs trace galaxies over a wide range of galaxy luminosities, however, the bulk of the DLA cross-section arises in galaxies with L ~ 0.1 L* at z ~ 2.5 broadly consistent with numerical simulations.