Detection of pairwise kSZ effect with DESI galaxy clusters and Planck

We report a 5 sigma detection of the pairwise kinematic Sunyaev-Zel'dovich (kSZ) effect, combining galaxy clusters in DESI imaging surveys and the Planck temperature maps. The detection is facilitated by both improvements in the data and in the analysis method. For the data, we adopt the recently released DESI galaxy group catalog with similar to 10(6) robustly identified groups, and construct various galaxy cluster samples for the kSZ measurement. The DESI group catalogue also provides estimation of halo mass, which further improves the kSZ measurement by similar to 10 per cent. For the analysis method, we derive an optimal estimator of pairwise kSZ through the maximum likelihood analysis. It also handles potential systematic errors self-consistently. The baseline cluster sample, containing the 1.2 x 10(5) richest galaxy clusters of typical mass similar to 10(14) M M-circle dot/h at typical redshift 0.2-0.5, rules out the null hypothesis at 5 sigma. When fitting with a pairwise kSZ template from simulations, the signal is detected at 4.7sand the average optical depth is constrained as (tau) over bar (e) = (1.66 +/- 0.35) x 10(-4). We perform various internal checks, with different cluster selection criteria, different sky coverage, and redshift range, different CMB maps, different filter sizes, different treatments of potential systematics, and the covariance matrix. The kSZ effect is consistently detected with 2.5 <= S/N <= 5.6 and acceptable chi(2)(min), across a variety of cluster samples. The S/N is limited by both the Planck resolution and the photo-z accuracy, and therefore, can be significant improved with DESI spectroscopic redshift information and with other CMB experiments.

Automated summary

We report a 5 sigma detection of the pairwise kinematic Sunyaev-Zel'dovich (kSZ) effect using a combination of galaxy clusters in DESI imaging surveys and the Planck temperature maps. The detection is achieved through improvements in data and analysis method, and it provides important information about the clusters. The study suggests that the signal of the kSZ effect can be significantly improved with additional DESI spectroscopic redshift information and other CMB experiments.