Measuring patchy reionization with kSZ^{2}21 cm correlations
Abstract
We study crosscorrelations of the kinetic SunyaevZel'dovich effect (kSZ) and 21 cm signals during the epoch of reionization (EoR) to measure the effects of patchy reionisation. Since the kSZ effect is proportional to the lineofsight velocity, the kSZ21 cm cross correlation suffers from cancellation at small angular scales. We thus focus on the correlation between the kSZsquared field (kSZ^{2}) and 21 cm signals. When the global ionization fraction is low (x_{e} ≲ 0.7), the kSZ^{2} fluctuation is dominated by rare ionized bubbles, which leads to an anticorrelation with the 21 cm signal. When 0.8 ≲ x_{e} < 1, the correlation is dominated by small pockets of neutral regions, leading to a positive correlation. However, at very high redshifts when x_{e} < 0.15, the spin temperature fluctuations change the sign of the correlation from negative to positive, as weakly ionized regions can have strong 21 cm signals in this case. To extract this correlation, we find that Wiener filtering is effective in removing large signals from the primary cosmic microwave background (CMB) anisotropy. The expected signaltonoise ratios for a ∼10h integration of upcoming Square Kilometre Array data crosscorrelated with maps from the current generation of CMB observatories with 3.4μK arcmin noise and 1.7 arcmin beam over 100 deg^{2} are 51, 60, and 37 for x_{e} = 0.2, 0.5, and 0.9, respectively.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 May 2018
 DOI:
 10.1093/mnras/sty543
 arXiv:
 arXiv:1712.05305
 Bibcode:
 2018MNRAS.476.4025M
 Keywords:

 cosmic background radiation;
 dark ages;
 reionization;
 first stars;
 early Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 7pages, 7 figures