An Improved Treatment of Cosmological Intergalactic Medium Evolution

TL;DR

This paper enhances the modeling of the intergalactic medium's evolution by refining the governing equations, incorporating detailed physical processes, and providing an analytic method for halo mass function calculation in ionized regions.

Contribution

It introduces improved equations for IGM phases, accounts for inflows/outflows, and offers an analytic approach for halo mass functions considering environmental ionization bias.

Findings

More accurate IGM phase modeling

Inclusion of inflows and outflows effects

Analytic halo mass function calculation

Abstract

The modeling of galaxy formation and reionization, two central issues of modern cosmology, relies on the accurate follow-up of the intergalactic medium (IGM). Unfortunately, owing to the complex nature of this medium, the differential equations governing its ionization state and temperature are only approximate. In this paper, we improve these master equations. We derive new expression for the distinct composite inhomogeneous IGM phases, including all relevant ionizing/recombining and cooling/heating mechanisms, taking into account inflows/outflows into/from halos, and using more accurate recombination coefficients. Furthermore, to better compute the source functions in the equations we provide an analytic procedure for calculating the halo mass function in ionized environments, accounting for the bias due to the ionization state of their environment. Such an improved treatment of IGM evolution is part of a complete realistic model of galaxy formation presented elsewhere.