Measuring transverse peculiar velocity of galaxy clusters

The peculiar velocity of galaxy clusters offers an alternative and effective way to constrain cosmology, particularly growth parameters and matter fluctuation amplitude. The peculiar velocity has two components — the radial and the transverse part. The radial part of the peculiar velocity imprints a kSZ (kinematic Sunyaev-Zel'dovich) signal on the background CMB. While the pairwise kSZ signal has been measured previously, it is limited by degeneracy with the optical depth.

In this work, we develop an optimal filter to extract the transverse moving lens effect. We quantify the systematic and statistical uncertainty for various foregrounds. We forecast the SNR for the ongoing Simons Observatory and the CMB-S4 experiment.