Translate 
Abstract
ABSTRACT A growing population of metal absorbers are observed at z > 5, many showing strong evolution in incidence approaching the epoch of hydrogen reionization. Follow-up surveys examining fields around these metals have resulted in galaxy detections but the direct physical relationship between the detected galaxies and absorbers is unclear. Upcoming observations will illuminate this galaxy–absorber relationship, but the theoretical framework for interpreting these observations is lacking. To inform future z > 5 studies, we define the expected relationship between metals and galaxies using the Technicolor Dawn simulation to model metal absorption from z = 5 to 7, encompassing the end of reionization. We find that metal absorber types and strengths are slightly better associated with their environment than with the traits of their host galaxies, as absorption system strengths are more strongly correlated with the local galaxy overdensity than the stellar mass of their host galaxy. For redshifts prior to the end of the epoch of reionization, strong high-ionization transitions like C iv are more spatially correlated with brighter galaxies on scales of a few hundred proper kpc than are low-ionization systems, due to the former’s preference for environments with higher ultraviolet background amplitudes and those ions’ relative rarity at z > 6. Post-reionization, the galaxy counts near these high-ionization ions are reduced, and increase surrounding certain low-ionization ions due to a combination of their relative abundances and preferred denser gas phase. We conclude that galaxy–absorber relationships are expected to evolve rapidly such that high-ionization absorbers are better tracers of galaxies pre-reionization, while low-ionization absorbers are better post-reionization.
Highlights
Warmer gas traced by for example C IV may increase in equivalent width (EW) and incidence with specific star formation rate (SFR) (sSFR), and shows a flatter profile with impact parameter than cool gas tracers (Oppenheimer & Dave 2008; Borthakur et al 2013; Bordoloi et al 2014; Liang & Chen 2014; Werk et al 2014; Rubin et al 2015; Dutta et al 2021; Manuwal et al 2021)
We describe the model predictions for the number and observability of galaxies around metal absorbers from z = 5 to 7, the relationships between metal absorbers and their host galaxy traits, and the characteristics of the environments probed by the metals
For z < 2, correlations are observed between metal absorbers and the characteristics of their host galaxies; we begin by looking for any such correlations in our simulated systems
Summary
Prior to the formation of the first stars gas is pristine and devoid of heavier elements, but once star formation begins at z ∼ 20 heavier metals are formed via various nucleosynthetic pathways. At lower redshifts (0 < z < 1), metals may be studied in tandem with nearby galaxies, especially those located within one to a few Rvir. Such studies suggest possible correlations between galaxy traits and the covering fraction, strength, and incidence of metal absorption systems. Low-ionization gas tracers like Mg II may show correlations in strength and incidence with the galaxy overdensity and with the impact parameter, stellar mass, star formation rate (SFR), and specific SFR (sSFR) of the apparent host galaxy (Chen et al 2010; Bordoloi et al 2011; Nielsen, Churchill & Kacprzak 2013; Nielsen et al 2018, 2021; Rubin et al 2018; Fossati et al 2019; Dutta et al 2020, 2021; Lundgren et al 2021). C IV may be less abundant and/or strong in the inner halo of massive galaxies (e.g. Burchett et al 2016)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
