How Neutral Is the Intergalactic Medium atz∼ 6?

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...

Radio Foregrounds for the 21cm Tomography of the Neutral Intergalactic Medium at High Redshifts

Absorption or emission against the cosmic microwave background radiation (CMB) may be observed in the redshifted 21cm line if the spin temperature of the neutral intergalactic medium prior to reionization differs from the CMB temperature. This so-called 21cm tomography should reveal important information on the physical state of the intergalactic medium at high redshifts. The fluctuations in th...

The thermal history of the intergalactic medium

At redshifts z2, most of the baryons reside in the smooth intergalactic medium which is responsible for the low column density Lyα forest. This photoheated gas follows a tight temperature-density relation which introduces a cut-off in the distribution of widths of the Lyα absorption lines (b-parameters) as a function of column density. We have measured this cut-off in a sample of nine high reso...

Measuring the Temperature 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 temperaturedensity relation. We show that such an equation of state results in a cutoff in the distribution of line widths (b-parameters) as a function of column density (N) for the low column density absorption lines. This explains the...