Constraints on Halo Gas Profiles from Joint kSZ and Galaxy Clustering Analysis of ACT DR6 and CMASS

TL;DR

This paper presents a joint analysis of kSZ and galaxy clustering data from ACT DR6 and CMASS to measure halo gas profiles, revealing a more extended gas distribution than simulations suggest.

Contribution

It introduces a method to reconstruct halo optical depth profiles by breaking degeneracies, providing new insights into baryonic feedback effects.

Findings

kSZ signal detected with S/N of 7.2 at 2 arcmin aperture

Full profile rejects no-kSZ hypothesis at 8.7 sigma

Observed gas profiles are more extended than in simulations

Abstract

We measure the kinetic Sunyaev-Zel'dovich (kSZ) signal through a joint analysis of the pairwise kSZ effect and galaxy clustering using CMASS galaxies and ACT DR6 maps. This approach breaks degeneracies between the optical depth and nuisance parameters, enabling a reconstruction of the halo optical depth profile as a function of aperture scale. The kSZ signal reaches its highest signal-to-noise ratio of 7.2 at an aperture radius of $\theta_{\rm AP} = 2$ arcmin, while the full profile rejects the no-kSZ hypothesis at $8.7\sigma$. Applying the same analysis pipeline to the Websky simulation, we find that the observed optical depth profile is somewhat more extended than the simulated one. This difference suggests that baryonic feedback in the real Universe may be stronger and redistribute gas to larger radii more efficiently than modeled in the simulation, although residual systematic effects and modeling uncertainties remain to be further investigated.