Damped Lyman alpha systems and disk galaxies: number density, column density distribution and gas density

TL;DR

This paper compares observed properties of damped Lyman alpha systems with simple models of disk galaxy evolution to estimate their contribution and explore the nature of non-disk galaxy DLAs.

Contribution

It provides a comparison between observed DLA properties and model predictions, estimating the contribution of disk galaxies to DLAs and discussing non-disk galaxy origins.

Findings

Disk galaxies contribute significantly to DLAs at various redshifts.

Differences between models and observations suggest some DLAs originate outside disk galaxies.

The study estimates the evolution of DLA properties with redshift.

Abstract

We present a comparison between the observed properties of damped Lyman alpha systems (DLAs) and the predictions of simple models for the evolution of present day disk galaxies, including both low and high surface brightness galaxies. We focus in particular on the number density, column density distribution and gas density of DLAs, which have now been measured in relatively large samples of absorbers. From the comparison we estimate the contribution of present day disk galaxies to the population of DLAs, and how it varies with redshift. Based on the differences between the models and the observations, we also speculate on the nature of the fraction of DLAs which apparently do not arise in disk galaxies.