Detection likelihood of cluster-induced CMB polarization

TL;DR

This paper assesses the detectability of polarization signals in the CMB induced by nearby galaxy clusters, considering instrumental noise and other factors, and finds that some signals are potentially observable with current or upcoming telescopes.

Contribution

It provides a feasibility analysis for detecting cluster-induced CMB polarization signals, including thermal and kinematic SZ effects, with realistic observational constraints.

Findings

Thermal SZ intensity can be mapped sensitively in rich nearby clusters.

Kinematic SZ intensity can be measured with high significance in fast-moving clusters.

Polarized SZ signals are challenging but potentially detectable in very rich nearby clusters.

Abstract

Nearby galaxy clusters can potentially induce sub-microkelvin polarization signals in the cosmic microwave background (CMB) at characteristic scales of a few arcminutes. We explore four such polarization signals induced in a rich nearby fiducial cluster and calculate the likelihood of their detection by a telescope project with capabilities such as those of the Simons Observatory (SO). In our feasibility analysis, we include instrumental noise, primordial CMB anisotropy, statistical thermal Sunyaev-Zeldovich (SZ) cluster signal, and point source confusion, assuming a few percent of the nominal telescope observation time of an SO-like project. Our analysis indicates that the thermal SZ intensity can be sensitively mapped in rich nearby clusters and that the kinematic SZ intensity can be measured with high statistical significance toward a fast moving nearby cluster. The detection of polarized SZ signals will be quite challenging but could still be feasible toward several very rich nearby clusters with very high SZ intensity. The polarized SZ signal from a sample of ~20 clusters can be statistically detected at S/N~3, if observed for several months.