Comparison of halo model and simulation predictions for projected-field kinematic Sunyaev-Zel'dovich cross-correlations

Abstract The kinematic Sunyaev-Zel'dovich (kSZ) effect in the cosmic microwave background (CMB) is a powerful probe of gas physics and large-scale structure (LSS) in our universe. Here we consider the “projected-field” kSZ estimator, which involves cross-correlating a foreground-cleaned, filtered, squared CMB temperature map with an LSS tracer, and requires no individual tracer redshifts. We compare class_sz halo model calculations of projected-field kSZ cross-correlations with measurements of these signals from the Websky numerical simulations. We extract dark matter halo catalogs from Websky and cross-correlate halo number density maps with various CMB secondary signals. We first validate our halo model by comparing its predictions for thermal SZ (tSZ) and patchy screening ( τ ) cross-correlations to measurements of these signals from Websky. We consider three different halo redshift ranges in our comparisons. We also construct our own kSZ, tSZ, and τ maps to validate the form of the relevant profiles. Following the tSZ and τ validation, we compare projected-field kSZ calculations between the halo model and the simulations. We use filters constructed for Planck and the Simons Observatory (SO) to assess the accuracy of the halo-model kSZ predictions for experiments of differing sensitivity. Overall, we find reasonable agreement, particularly at Planck sensitivity. However, we find an ≈ 50% difference between our halo model and the simulation measurements for SO, which significantly exceeds the predicted error bars. We note that our halo model includes only the dominant expected term in the projected-field kSZ signal; the magnitude of the difference between our model and the simulations is consistent with previous predictions for terms arising from other contractions in the theory calculation. These terms will need to be included to obtain unbiased inference from upcoming projected-field kSZ measurements.