Through Thick and Thin - HI Absorption in Cosmological Simulations

Abstract

We investigate the column density distribution function of neutral hydrogen at redshift z = 3 using a cosmological simulation of galaxy formation from the OverWhelmingly Large Simulations (OWLS) project. The base simulation includes gravity, hydrodynamics, star formation, supernovae feedback, stellar winds, chemodynamics, and element-by-element cooling in the presence of a uniform UV background. Self-shielding and formation of molecular hydrogen are treated in post-processing, without introducing any free parameters, using an accurate reverse ray-tracing algorithm and an empirical relation between gas pressure and molecular mass fraction. The simulation reproduces the observed z = 3 abundance of Ly-A forest, Lyman Limit and Damped Ly-A HI absorption systems probed by quasar sight lines over ten orders of magnitude in column density. Self-shielding flattens the column density distribution for NHI > 10^18 cm-2, while the conversion to fully neutral gas and conversion of HI to H2 steepen it around column densities of NHI = 10^20.3 cm-2 and NHI = 10^21.5 cm-2, respectively.

updated to match ApJL accepted version. now includes line list for fiducial model

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• IGM Constraints from the SDSS-III/BOSS DR9 Ly-alpha Forest Flux Probability Distribution Function
• Modeling the neutral hydrogen distribution in the post-reionization Universe: intensity mapping
• Witnessing galaxy assembly in an extended z~3 structure
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• Linking gas and galaxies at high redshift: MUSE surveys the environments of six damped Lyman alpha galaxies at z~3
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• The broadening of Lyman-alpha forest absorption lines
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• Rabacus: A Python Package for Analytic Cosmological Radiative Transfer Calculations