http://arxiv.org/abs/1403.0221
Using hydrodynamical simulations coupled to a 1D radiative transfer code, we study the additional heating effects produced by $z\sim6$ QSOs in their near-zones. We show that both normalization ($T_0$) and slope ($\gamma$) of the intergalactic medium (IGM) effective equation-of-state get modified by the excess ionization from the quasars. However, the extent of this effect depends on the physical conditions prevailing in the IGM prior to the quasar era. We show, with a sample size similar to the presently available data, that it will be relatively easier to detect the change in $T_0$ compared to that in $\gamma$. Using the available constraints on $T_0$ at $z\sim6$, we discuss implications for the nature and epoch of HI and HeII reionization. We study the extent of He III region as a function of quasar age and show, for a typical inferred age of $z\sim6$ QSOs (i.e $\sim 10^8$ yrs), it extends up to 80 per cent of the HI proximity region. This is also the time-scale over which the temperature in most of the near-zone saturates and becomes distance independent. This implies that even when one uses all the HI lines in the QSO proximity region, the heating effects can be detected as long as the QSO age is sufficiently large. Using flux and curvature probability distribution functions (pdfs), we study the statistical detectability of heating effects as a function of initial physical conditions prevailing in the IGM. We show that for the present sample size, cosmic variance dominates the flux pdf. The curvature statistics is more suited to capturing the heating effects beyond the cosmic variance, even if the sample size is half of what is presently available.
H. Padmanabhan, T. Choudhury and R. Srianand
Tue, 4 Mar 14
23/61