Projected-Field Kinetic Sunyaev-Zel'dovich Cross-Correlations: Halo Model and Forecasts

The kinetic Sunyaev-Zel’dovich (kSZ) effect, i.e., the Doppler boost of cosmic microwave background (CMB) photons caused by their scattering off free electrons in galaxy clusters and groups with non-zero bulk velocity, is a powerful window on baryons in the universe. We present the first halo-model computation of the cross-power spectrum of the ``projected-field’’ kSZ signal with large-scale structure (LSS) tracers. We compare and validate our calculations against previous studies, which relied on $N$-body-calibrated effective formulas rather than the halo model. We forecast results for CMB maps from the Atacama Cosmology Telescope (AdvACT), Simons Observatory (SO), and CMB-S4, and LSS survey data from the Dark Energy Survey, the Vera C.~Rubin Observatory (VRO), and $\mathit{\text{Euclid}}$. In cross-correlation with galaxy number density, for AdvACT $\times$ $\mathit{\text{unWISE}}$ we forecast an 18$\sigma$ projected-field kSZ detection using data already in hand. Combining SO CMB maps and $\mathit{\text{unWISE}}$ galaxy catalogs, we expect a $62\sigma$ detection, yielding precise measurements of the gas density profile radial slopes. Additionally, we forecast first detections of the kSZ – galaxy weak lensing cross-correlation with AdvACT $\times$ VRO/$\mathit{\text{Euclid}}$ (at 6$\sigma$) and of the kSZ – CMB weak lensing cross-correlation with SO (at 16$\sigma$). Finally, $\approx 10-20$% precision measurements of the shape of the gas density profile should be possible with CMB-S4 kSZ – CMB lensing cross-correlation without using any external datasets.