Galaxy-Absorber Association in the Epoch of Reionization: Galactic Population Luminosity Distribution for Different Absorbers at $10 \geq z \geq 5.5$

TL;DR

This study analyzes how galaxies of different luminosities and masses contribute to metal absorption lines during the Epoch of Reionization, revealing that galaxy mass influences metal contribution more than luminosity.

Contribution

It introduces the Host Galaxy Luminosity Distribution (HGLD) and Host Galaxy Mass Distribution (HGMD) as tools to link absorbers to galaxy properties during reionization.

Findings

HGLD shape matches the field luminosity function, indicating no direct relation between absorber strength and galaxy luminosity.

More massive galaxies contribute more to metal absorbers, especially for stronger absorbers.

Observational trends are more likely to correlate with stellar mass than with luminosity.

Abstract

How do galaxies of different luminosities contribute to the metal absorber populations of varying species and strength? We present our analysis of the predicted metal contributions from galaxies as observed in quasar absorption line spectra during the end of the Epoch of Reionization (EoR; $10 \geq z \geq 5.5$). This was done by implementing on-the-fly particle tracking into the latest \textsc{Technicolor Dawn} simulation and then linking CII, CIV, SiII, SiIV, OI, and MgII absorbers to host galaxies in post-processing. We define the Host Galaxy Luminosity Distribution (HGLD) as the rest-frame ultraviolet luminosity distribution of galaxies contributing ions to an absorber, weighted by the fractional contribution, and compute its dependence on ion and absorber strength. The HGLD shape is predicted to be indistinguishable from the field luminosity function, indicating that there is no relationship between the absorber strength or ion and the luminosity of the dominant contributing galaxy. Switching from galaxy luminosity to stellar mass, the predicted host galaxy mass distributions (HGMD) indicate that more-massive galaxies contribute a higher fraction of metal ions to absorbers of each species, with the HGMD of stronger absorbers extending out to higher masses. We conclude that the fraction of absorbing metal ions contributed by galaxies increases weakly with stellar mass, but the scatter in luminosity at fixed stellar mass obscures this relationship. For the same reason, we predict that observational analyses of the absorber-galaxy relationship will uncover stronger trends with stellar mass than with luminosity.