The Evolution of the Effective Equation of State of the Intergalactic Medium

Abstract
We develop a method to extract the "effective equation of state" of the intergalactic medium from the Doppler (b) parameter distribution of the low-density Lyα forest. We test the method on numerical simulations and then apply it to published observations of the Lyα forest at redshifts z 0-4. We find that the effective equation of state is close to isothermal at redshift z ~ 3, indicating that a second reheating of the intergalactic medium took place at z ~ 3. This reheating can plausibly be identified with the reionization of He II observed to occur at z ~ 3.

This publication has 34 references indexed in Scilit: