Measurement of the galaxy-velocity power spectrum of DESI tracers with the kinematic Sunyaev-Zeldovich effect using DESI DR2 and ACT DR6

TL;DR

This paper presents the first detection of galaxy velocity correlations using the kSZ effect with DESI and ACT data, providing new constraints on primordial non-Gaussianity and demonstrating the potential of velocity-based observables for future cosmology.

Contribution

It introduces the first measurements of velocity-galaxy and velocity-velocity correlations using high-resolution CMB and galaxy survey data, improving constraints on primordial non-Gaussianity.

Findings

Detected velocity-galaxy cross-correlation at 17.0σ for LRGs.

First detection of velocity-velocity correlation at 3.1σ for LRGs.

Achieved the highest cumulative detection of the kSZ effect at 20.8σ.

Abstract

Joint analyses of high-resolution CMB temperature maps with galaxy surveys provide a unique way to reconstruct the radial velocity field of the underlying matter distribution via the kinematic Sunyaev-Zeldovich (kSZ) effect. Using data from the Atacama Cosmology Telescope (ACT) DR6 and the Dark Energy Spectroscopic Instrument (DESI) DR2, we present radial velocity reconstructions for luminous red galaxies (LRGs), emission-line galaxies (ELGs), and quasars (QSOs). Leveraging the spectroscopic data, we are able to reliably model the foreground contamination and report a negligible impact on our main observables. We detect the velocity-galaxy cross-correlation at $17.0\sigma$ for LRGs, and for the first time, at $8.3\sigma$ for ELGs and $6.8\sigma$ for QSOs. We further report the first detection of the velocity-velocity correlation using LRGs at $3.1\sigma$, as well as the highest cumulative detection of the kSZ effect to date at $20.8 \sigma$. Similarly to previous results, we find a lower amplitude of the kSZ signal compared to our fiducial halo model prediction and electron profile assuming a Battaglia profile. Combining these new observables, we obtain constraints on local-type primordial non-Gaussianity (PNG): $f_{\rm NL}^{\rm loc} = 15.9_{-34.4}^{+34.6}$ at 68\% confidence, which represents the tightest constraint to date derived from the velocity field. The measurements presented here already exhibit lower noise on a per-mode basis than the galaxy auto-correlation on the largest scales, $k<0.004~\rm{Mpc^{-1}}$, highlighting the key role these observables will play in the context of future CMB experiments such as the Simons Observatory.