Physical state of the intergalactic medium at redshiftsz= 2-4

The Physical State of the Intergalactic Medium or Can We Measure Y ?

We present an argument for a lower limit to the Compton-y parameter describing spectral distortions of the cosmic microwave background (CMB). The absence of a detectable Gunn-Peterson signal in the spectra of high redshift quasars demands a high ionization state of the intergalactic medium (IGM). Given an ionizing flux at the lower end of the range indicated by the proximity effect, an IGM repr...

Measuring the equation of state of the intergalactic medium

Numerical simulations indicate that the smooth, photoionized intergalactic medium (IGM) responsible for the low column density Lyα forest follows a well defined temperature-density relation, which is well described by a power-law T = T0(ρ/ρ̄)γ−1. We demonstrate that such an equation of state results in a power-law cutoff in the distribution of line widths (b-parameters) as a function of column d...

Equation of State of the Photoionized Intergalactic Medium

We develop an efficient method to study the effects of reionization history on the temperature-density relation of the intergalactic medium in the low density limit (overdensity δ < ∼ 5). It is applied to the study of photo-reionization models in which the amplitude, spectrum and onset epoch of the ionizing flux, as well as the cosmology, are systematically varied. We find that the mean tempera...

Intergalactic Medium

Simulations of the Intergalactic Medium

I present a review by epoch of baryons in the intergalac-tic medium (IGM), from the first star until today. Recent observations indicate a protracted period of reionization, suggesting multiple populations of reionizers; detection of these z ∼ > 6 sources is a key goal that is now coming within reach. The optical Lyman alpha forest (2 ∼ < z ∼ < 4) is well-described by the Fluctuating Gunn-Peter...