Kinetic Sunyaev-Zel'dovich tomography with line-intensity mapping
Abstract
The kinetic Sunyaev-Zel'dovich (kSZ) effect is a secondary cosmic microwave background (CMB) anisotropy induced by the scattering of CMB photons off intervening electrons. Through cross-correlations with tracers of large-scale structure, the kSZ effect can be used to reconstruct the 3-dimensional radial-velocity field, a technique known as kSZ tomography. We explore the cross-correlation between the CMB and line-intensity fluctuations to retrieve the late-time kSZ signal across a wide redshift range. We focus on the CII emission line, and predict the signal-to-noise ratio of the kSZ tomography signal between redshifts z=1-5 for upcoming experiments. We show that while instruments currently under construction may reach a low-significance detection of kSZ tomography, next-generation experiments will achieve greater sensitivity, with a detection significance of O(102-103). Due to sample-variance cancellation, the cross-correlation between the reconstructed velocity field from kSZ tomography and intensity fluctuations can improve measurements of %the scale-dependent bias contributions from new physics to the power spectrum at large scales. To illustrate this improvement, we consider models of the early Universe that induce primordial local-type non-gaussianity and correlated compensated isocurvature perturbations. We show that with CMB-S4 and an AtLAST-like survey, the uncertainty on f NL and A CIP can be reduced by a factor of 3, achieving σ(f NL) 1. We further show that probing both low and high redshifts is crucial to break the degeneracy between the two parameters.