Prospects for kSZ2-Galaxy Cross-correlations during Reionization

• Main Authors: La Plante, P. (Author), Lidz, A. (Author), Sipple, J. (Author)
• Format: Article
• Language: English
• Published: IOP Publishing Ltd 2022
• Online Access: View Fulltext in Publisher

 We explore a new approach for extracting reionization-era contributions to the kinetic Sunyaev-Zel'dovich (kSZ) effect. Our method utilizes the cross-power spectrum between filtered and squared maps of the cosmic microwave background (CMB) and photometric galaxy surveys during the Epoch of Reionization (EoR). This kSZ2-galaxy cross-power spectrum statistic has been successfully detected at lower redshifts (z ≲ 1.5). Here we extend this method to z ≳ 6 as a potential means to extract signatures of patchy reionization. We model the expected signal across multiple photometric redshift bins using seminumeric simulations of the reionization process. In principle, the cross-correlation statistic robustly extracts reionization-era contributions to the kSZ signal, while its redshift evolution yields valuable information regarding the timing of reionization. Specifically, the model cross-correlation signal near ℓ ∼1000 peaks during the early stages of the EoR, when about 20% of the volume of the universe is ionized. Detectable ℓ modes mainly reflect squeezed-triangle configurations of the related bispectrum, quantifying correlations between the galaxy overdensity field on large scales and the smaller-scale kSZ power. We forecast the prospects for detecting this signal using future wide-field samples of Lyman-break galaxies from the Roman Space Telescope and next-generation CMB surveys including the Simons Observatory, CMB-S4, and CMB-HD. We find that a roughly 13σ detection is possible for CMB-HD and Roman after summing over all ℓ modes. We discuss the possibilities for improving this approach and related statistics, with the aim of moving beyond simple detections to measure the scale and redshift dependence of the cross-correlation signals. © 2022. The Author(s). Published by the American Astronomical Society.