The Atacama Cosmology Telescope: Detection of the pairwise kinematic Sunyaev-Zel’dovich effect with SDSS DR15 galaxies

Abstract

We present a 5.4σ detection of the pairwise kinematic Sunyaev-Zeldovich (kSZ) effect using Atacama Cosmology Telescope (ACT) and Planck CMB observations in combination with Luminous Red Galaxy samples from the Sloan Digital Sky Survey (SDSS) DR15 catalog. Results are obtained using three ACT CMB maps: co-added 150 and 98 GHz maps, combining observations from 2008-2018 (ACT DR5), which overlap with SDSS DR15 over 3,700 sq. deg., and a component-separated map using night-time only observations from 2014-2015 (ACT DR4), overlapping with SDSS DR15 over 2,089 sq. deg. Comparisons of the results from these three maps provide consistency checks in relation to potential frequencydependent foreground contamination. A total of 343,647 galaxies are used as tracers to identify and locate galaxy groups and clusters from which the kSZ signal is extracted using aperture photometry. We consider the impact of various aperture photometry assumptions and covariance estimation methods on the signal extraction. Theoretical predictions of the pairwise velocities are used to obtain best-fit, mass-averaged, optical depth estimates for each of five luminosity-selected tracer samples. A comparison of the kSZderived optical depth measurements obtained here to those derived from the thermal SZ effect for the same sample is presented in a companion paper.

Galaxy Cluster Statistics in Modified Gravity Cosmologies

“…Cluster velocities along the line of sight induce the kinematic Sunyaev-Zeldovich temperature shift in the microwave background; this signal has been detected directly via the mean pairwise momentum statistic [13,[37][38][39][40] and by cross-correlating with a cosmic velocity field inferred from the large-scale galaxy distribution [41]. Extracting cluster velocities from the kSZ signal is complicated by the signal being proportional to the bulk gas momentum rather than velocity; any claimed signature of modified gravity might also arise as a systematic error in cluster gas modeling.…”

“…The tSZ effect, which creates a spectral distortion in the microwave radiation passing through the galaxy cluster's ionized gas, is essentially independent of cluster redshift and gives a relatively simple selection function for clusters [9,10]. Once identified, cluster positions can be determined in three dimensions through follow-up galaxy redshift observations; cluster masses can be measured using optical weak gravitational lensing, such as [11], or statistically using lensing of the microwave background [12]; and cluster velocities can potentially be obtained from the kinematic Sunyaev-Zeldovich effect [13,14] or potentially from the transverse lensing effect [15]. As we anticipate a new generation of microwave experiments with steadily increasing sensitivity, quantifying the possibilities for constraining modified gravity is of particular interest.…”

Cosmology with the kinetic Sunyaev-Zeldovich effect: Independent of the optical depth and $σ_8$

“…One of the approaches to detect the kSZ signal is to employ the pairwise statistic (e.g. Hand et al 2012;Hernández-Monteagudo et al 2015;Planck Collaboration et al 2016;Schaan et al 2016;Soergel et al 2016;De Bernardis et al 2017;Li et al 2018;Calafut et al 2021;Chen et al 2021). There have been evidences of kSZ signal using other techniques also (e.g.…”

Probing the circumgalactic medium with CMB polarization statistical anisotropy

“…Other kSZ estimators such as the projected fields estimator (Hill et al 2016;Ferraro et al 2016;Kusiak et al 2021), the tomographic kSZ estimator (Shao & Fang 2016), and the pairwise kSZ estimator (e.g., De Bernardis et al 2017;Calafut et al 2021;Vavagiakis et al 2021) can further provide integral constraints optical depth of halos (the baryon abundance). Though the statistical properties of the optical depth of halos can be inferred only from such kSZ measurements, these crosscorrelation techniques reduce various systematic effects.…”