Institute for Advanced Study Informal Astrophysics Seminar

Observations of the intergalactic medium (IGM) suggest that quasars reionize the HeII at z ~ 3. HeII reionization heats the IGM by tens of thousands of Kelvin, and it affects the statistics of the HI and HeII Lyman-alpha forests. I will present a set of simulations of HeII being reionized by quasars. These simulations lead to a different picture for this process than in previous studies. If quasars have a mean spectral index of 1.5, I find that HeII reionization heats regions in the IGM by as much as 30,000 K above the temperature that is expected otherwise, with the volume-averaged temperature increasing by ~10,000 K and with large temperature fluctuations on ~50 comoving Mpc scales. However, the amount of heating can be much larger if the spectrum is harder. I discuss how temperature fluctuations from HeII reionization bias measurements from the HI Lyman-alpha forest of the IGM temperature and of cosmological parameters, and I quantify the detectability of these fluctuations with wavelet statistics. I conclude by contrasting the morphology of HeII reionization by quasars with that of hydrogen reionization by stars.