Kinetic Sunyaev-Zeldovich (kSZ) velocity reconstruction
In this paper we developed a new technique, called kSZ velocity reconstruction (sometimes also kSZ tomography), that uses the non-linear secondary anisotropies of the CMB, in combination with a galaxy survey, to get tighter constraints on cosmological parameters. The kSZ effect, the scattering of CMB photons on moving electrons, is the leading contribution to the CMB at small scales and a main observational target of upcoming CMB experiments. Prior to our work the kSZ was considered interesting mostly for small-scale astrophysics. However, by cross-correlating CMB measurements with a galaxy survey, one can reconstruct the large-scale matter velocity field with high signal-to-noise. The velocity field reconstructed with kSZ has cosmological applications similar to the much more well studied lensing map and has high signal-to-noise for upcoming experiments (forecasted in our paper, e.g. Simons Observatory plus DESI total SNR~400). This provides a new cosmological observable is found that is powerful already with near-term experiments.