Predictions for the relation between strong Hi absorbers and galaxies at redshift 3

• Published in: Monthly notices of the Royal Astronomical Society 2014-02, Vol.438 (1), p.529-547
• Main Authors: Rahmati, Alireza, Schaye, Joop
• Format: Article
• Language: English
• Subjects: Astronomy; Cosmology; Star & galaxy formation
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stt2235

We combine cosmological, hydrodynamical simulations with accurate radiative transfer corrections to investigate the relation between strong absorbers ( ) and galaxies at redshift z = 3. We find a strong anticorrelation between the column density and the impact parameter that connects the absorber to the nearest galaxy. The median impact parameters for Lyman Limit (LL) and Damped Lyman α systems (DLAs) are ∼10 and ∼1 proper kpc, respectively. If normalized to the size of the halo of the nearest central galaxy, the median impact parameters for LL and DLA systems become ∼1 and ∼10−1 virial radii, respectively. At a given column density, the impact parameter increases with the mass of the closest galaxy, in agreement with observations. We predict most strong absorbers to be most closely associated with extremely low-mass galaxies, M < 108 M and star formation rate < 10− 1 M yr− 1. We also find a correlation between the column density of absorbers and the mass of the nearest galaxy. This correlation is most pronounced for DLAs with 10^{21} \,{\rm cm^{-2}}$]]> which are typically close to galaxies with M 109 M. Similar correlations exist between column density and other properties of the associated galaxies such as their star formation rates, halo masses and content. The galaxies nearest to absorbers are typically far too faint to be detectable with current instrumentation, which is consistent with the high rate of (often unpublished) non-detections in observational searches for the galaxy counterparts of strong absorbers. Moreover, we predict that the detected nearby galaxies are typically not the galaxies that are most closely associated with the absorbers; thus, causing the impact parameters, star formation rates and stellar masses of the observed counterparts to be biased high.