2023/11/29 by Tortora, Lucas, Feldmann, Robert, Bernardini, Mauro +1
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2311.18000
Atomic hydrogen (HI) serves a crucial role in connecting galactic-scale properties such as star formation with the large-scale structure of the Universe. While recent numerical simulations have successfully matched the observed covering fraction of HI near Lyman Break Galaxies (LBGs) and in the foreground of luminous quasars at redshifts z \lesssim 3, the low-mass end remains as-of-yet unexplored in observational and computational surveys. We employ a cosmological, hydrodynamical simulation (FIREbox) supplemented with zoom-in simulations (MassiveFIRE) from the Feedback In Realistic Environments (FIRE) project to investigate the HI covering fraction of Lyman Limit Systems (NHI \gtrsim 1017.2 cm-2) across a wide range of redshifts (z=0-6) and halo masses (108-1013 M\odot at z=0, 108-1011 M\odot at z=6) in the absence of feedback from active galactic nuclei. We find that the covering fraction inside haloes exhibits a strong increase with redshift, with only a weak dependence on halo mass for higher-mass haloes. For massive haloes (Mvir ∼ 1011-1012 M\odot), the radial profiles showcase scale-invariance and remain independent of mass. The radial dependence is well-captured by a fitting function. The covering fractions in our simulations are in good agreement with measurements of the covering fraction in LBGs. Our comprehensive analysis unveils a complex dependence with redshift and halo mass for haloes with Mvir \lesssim 1010 M\odot that future observations aim to constrain, providing key insights into the physics of structure formation and gas assembly.