Mapping the gas density with the kinematic Sunyaev-Zel'dovich and patchy screening effects: a self-consistent comparison

TL;DR

This paper measures gas density around galaxies using CMB secondary anisotropies, detecting the kSZ and patchy screening effects, and accounts for lensing contamination to constrain optical depth and baryonic feedback.

Contribution

It provides a self-consistent comparison of kSZ and patchy screening effects, demonstrating the impact of lensing contamination and establishing upper bounds on optical depth.

Findings

Detected kSZ at 7.2σ significance

Detected patchy screening at 4.1σ significance

Lensing contamination dominates the screening signal

Abstract

The secondary anisotropies of the cosmic microwave background (CMB) provide a wealth of astrophysical and cosmological information. Pairing measurements of the CMB temperature map obtained by DR5 of the Atacama Cosmology Telescope (ACT) with the large-scale structure imaging survey conducted by the Dark Energy Spectroscopic Instrument, DECaLS DR9, we investigate two effects that are sensitive to the gas density $\tau$: kinematic Sunyaev-Zel'dovich (kSZ) and `patchy screening' (also known as `anisotropic screening'). In particular, we measure the stacked profiles around Luminous Red Galaxies (LRGs) at a mean redshift of $z \approx 0.7$. We detect the kSZ signal at 7.2$\sigma$, and we find a signal at $\sim 4.1\sigma$ for the patchy screening estimator, which is in excess relative to the kSZ signal. We attribute this excess to contamination from CMB lensing. We demonstrate the effect of lensing using $N$-body simulations, and we show that the screening signal is dominated by it. Accounting for lensing, our measurement places a 95\% upper bound on the optical depth of the Extended DESI LRG sample of $\tau <$ 2.5 $10^{-4}$ for a mean value of the sample of $\tau \approx$ 1.6 $10^{-4}$. Furthermore, via hydro simulations, we show that the underlying optical depth signal measured by both effects (after removing the CMB lensing contribution) is in perfect agreement when adopting either a Compensated Aperture Photometry (CAP) filter or a high-pass filter. Consistent with previous measurements, we see evidence for excess baryonic feedback around DESI LRGs in the patchy screening measurement. Provided both effects are measured with high signal-to-noise, one can measure the amplitude ratio between them, which is proportional to the root-mean-square velocity of the host halo sample, and place constraints on velocity-sensitive models such as modified gravity and phantom dark energy.