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

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 symetric collapse simulations spanning a large parameter space, we study the impact of an ultraviolet background (UVB) on the condensation of baryons onto dark matter haloes. We present an expression for the halo baryon fraction, f_b, which is an explicit function of (i) halo mass, (ii) UVB intensity, (iii) redshift and (iv) redshift at which the halo was exposed to a UVB. We also present a corresponding expression for the characteristic or critical mass, M_crit, 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.