Evidence for the kinematic Sunyaev-Ze\v{l}dovich effect with ACTPol and velocity reconstruction from BOSS

TL;DR

This paper detects the kinematic Sunyaev-Zel'dovich effect using ACTPol microwave maps and galaxy velocity reconstructions from BOSS, providing evidence at nearly 3 sigma significance for the effect over a specific redshift range.

Contribution

It presents the first measurement of the kSZ effect combining ACTPol data with galaxy velocity reconstruction from BOSS, achieving significant detection.

Findings

kSZ effect detected at 3.3 sigma significance

velocity reconstruction methods yield consistent results

foreground and thermal SZ contamination are effectively mitigated

Abstract

We use microwave temperature maps from two seasons of data from the Atacama Cosmology Telescope (ACTPol) at 146 GHz, together with the Constant Mass CMASS galaxy sample from the Baryon Oscillation Spectroscopic Survey to measure the kinematic Sunyaev-Ze\v{l}dovich (kSZ) effect over the redshift range z = 0.4 - 0.7. We use galaxy positions and the continuity equation to obtain a reconstruction of the line-of-sight velocity field. We stack the cosmic microwave background temperature at the location of each halo, weighted by the corresponding reconstructed velocity. The resulting best fit kSZ model is preferred over the no-kSZ hypothesis at 3.3sigma and 2.9sigma for two independent velocity reconstruction methods, using 25,537 galaxies over 660 square degrees. The effect of foregrounds that are uncorrelated with the galaxy velocities is expected to be well below our signal, and residual thermal Sunyaev-Ze\v{l}dovich contamination is controlled by masking the most massive clusters. Finally, we discuss the systematics involved in converting our measurement of the kSZ amplitude into the mean free electron fraction of the halos in our sample.