The origin of dispersion in DLA metallicities

TL;DR

This paper investigates the origins of metallicity dispersion in damped Ly-alpha absorbers by modeling how environmental differences in structure formation influence their chemical evolution, accounting for about half of the observed scatter.

Contribution

It introduces a semi-analytic model linking environmental structure formation to DLA metallicity variations, explaining the intrinsic scatter observed in measurements.

Findings

Environmental effects contribute ~0.25 dex to metallicity scatter.

Different structure formation histories influence DLA chemical properties.

Model reproduces observed metallicity-redshift relations.

Abstract

Recent chemical abundance measurements of damped Ly-alpha absorbers (DLAs) revealed an intrinsic scatter in their metallicity of ~0.5 dex out to z~5. In order to explore the origin of this scatter, we build a semi-analytic model which traces the chemical evolution of the interstellar matter in small regions of the Universe with different mean density, from over- to underdense regions. We show that the different histories of structure formation in these regions, namely halo abundance, mass and stellar content, is reflected in the chemical properties of the protogalaxies, and in particular of DLAs. We calculate mean metallicity-redshift relations and show that the metallicity dispersion arising from this environmental effect amounts to ~0.25 dex and is an important contributor to the observed overall intrinsic scatter.