Reionization observables after WMAP 3-year results

We use large-scale simulations of cosmic reionization to study the effect of varying the fundamental cosmological parameters on the reionization signatures. We compare two cases, one based on the WMAP 3-year data (WMAP3) characterized by a low σ8 = 0.74 and one motivated by the WMAP 1-year data (WMAP1) with a high σ8 = 0.9; dwarf galaxy formation is delayed by about 30% in redshift in the low σ8 case. Current cosmological parameter estimates synthesizing all of the available data indicate these two cases should bracket the full range of dwarf galaxy formation epochs relevant to reionization. In WMAP3 cosmology reionization is delayed, resulting in all 21-cm signatures moving to significantly higher frequencies. This should significantly facilitate the redshifted 21-cm observations compared to previous expectations, due to the diminishing foregrounds and the rising instrument sensitivities at higher frequencies. We find that for WMAP3 the best frequency range for observing the “global step” of the 21-cm emission is 120-150 MHz, while statistical studies should aim at 140-160 MHz, observable by GMRT. Some strongly-nongaussian brightness features are observable at frequencies up to ∼ 190 MHz. In terms of sensitivity-signal trade-off relatively low resolutions, corresponding to beams of at least a few arcminutes, are preferable. The CMB anisotropies due to patchy reionization have similar shape, but lower amplitude by factor of a few for WMAP3 compared to WMAP1. The signal peaks at tens of μK at arcminute scales and has an rms of ∼ 1μK and should be observable by Atacama Cosmology Telescope and South Pole Telescope in both σ8 cases.