The circumgalactic medium of high redshift galaxies

TL;DR

This study models the circumgalactic medium of high-redshift galaxies, revealing self-similar density profiles and an analytical relation for hydrogen absorption, aligning well with observations and suggesting minimal evolution over cosmic time.

Contribution

It introduces a simple analytical model for the CGM's hydrogen absorption profile that matches simulations and observations across different redshifts.

Findings

CGM gas density profiles are self-similar when scaled by virial radius.

An analytical expression relates neutral hydrogen equivalent width to impact parameter.

The model accurately reproduces observed hydrogen absorption profiles in galaxies.

Abstract

We study the properties of the circumgalactic medium (CGM) of high-$z$ galaxies in the metal enrichment simulations presented in Pallottini et al. 2014. At $z=4$, we find that the simulated CGM gas density profiles are self-similar, once scaled with the virial radius of the parent dark matter halo. We also find a simple analytical expression relating the neutral hydrogen equivalent width (${\rm EW}_{\rm HI}$) of CGM absorbers as a function of the line of sight impact parameter ($b$). We test our predictions against mock spectra extracted from the simulations, and show that the model reproduces the ${\rm EW}_{\rm HI}(b)$ profile extracted from the synthetic spectra analysis. When compared with available data, our CGM model nicely predicts the observed ${\rm EW}_{\rm HI}(b)$ in $z\lesssim2$ galaxies, and supports the idea that the CGM profile does not evolve with redshift.