The depletion of gas in high-redshift dwarf galaxies from an inhomogeneous reionization

TL;DR

This paper investigates how inhomogeneous reionization and UV background radiation deplete gas in high-redshift dwarf galaxies, affecting their growth by providing a new analytical model for baryon retention based on simulations.

Contribution

It introduces a new explicit formula for the halo baryon fraction considering UVB effects, applicable to inhomogeneous reionization scenarios.

Findings

Derived an expression for halo baryon fraction as a function of key parameters.

Identified the critical halo mass retaining half of its baryons.

Provided a model applicable to various reionization inhomogeneity conditions.

Abstract

The reionization of the intergalactic medium (IGM) was likely inhomogeneous and extended. By heating the IGM and photo-evaporating gas from the outskirts of galaxies, this process can have a dramatic impact on the growth of structures. Using a suite of spherically-symmetric collapse simulations spanning a large parameter space, we study the impact of an ionizing ultraviolet background (UVB) on the condensation of baryons onto dark matter halos. We present an expression for the halo baryon fraction, which is an explicit function of: (i) halo mass; (ii) UVB intensity; (iii) redshift; (iv) redshift at which the halo was exposed to a UVB. We also present a corresponding expression for the characteristic or critical mass, defined as the halo mass which retains half of its baryons compared to the global value. Since our results are general and physically-motivated, they can be broadly applied to inhomogeneous reionization models.