Constraints on the SZ Power Spectrum on Degree Angular Scales in WMAP Data

TL;DR

This paper constrains the Sunyaev-Zel'dovich effect's fluctuations on degree scales using WMAP data, finding an asymmetric signal that cannot be explained by known foregrounds or instrumental noise.

Contribution

It provides new upper bounds on SZ fluctuations at large scales and reports evidence of hemispheric asymmetry in the signal.

Findings

Upper bounds on SZ fluctuations at multipoles >50

Evidence for hemispheric asymmetry at 10-degree scales

Inability to explain the excess with known foregrounds or instrumental effects

Abstract

The Sunyaev-Zel'dovich (SZ) effect has a distinct spectral signature that allows its separation from fluctuations in the cosmic microwave background (CMB) and foregrounds. Using CMB anisotropies measured in Wilkinson Microwave Anisotropy Probe's five-year maps, we constrain the SZ fluctuations at large, degree angular scales corresponding to multipoles in the range from 10 to 400. We provide upper bounds on SZ fluctuations at multipoles greater than 50, and find evidence for a hemispherically asymmetric signal at ten degrees angular scales. The amplitude of the detected signal cannot be easily explained with the allowed number density and temperature of electrons in the Galactic halo. We have failed to explain the excess signal as a residual from known Galactic foregrounds or instrumental uncertainties such as 1/f-noise.