The Cross-correlation of KSZ Effect and 21 cm Intensity Mapping with Tidal Reconstruction

Understand

We discuss the possibility of studying diffuse baryon distributions with kinematic Sunyaev-Zel'dovich (kSZ) effect by correlating cosmic microwave background (CMB) temperature fluctuations with density fluctuations from 21\,cm intensity mapping (IM).

• The biggest challenge for the cross-correlation is the loss of large-scale information in IM, due to foregrounds and the zero spacing problem of interferometers.
• We apply the tidal reconstruction algorithm to restore the lost large-scale modes, which increases the correlation by more than a factor of three.
• With the predicted foreground level, we expect a $\sim20\,\sigma$ detection of kSZ signal for $0.8\lesssim z\lesssim2.5$ with CHIME and Planck, and a $\sim40\, \sigma$ detection with HIRAX and Planck.