Analysis of WMAP 7-year Temperature Data: Astrophysics of the Galactic Haze

TL;DR

This paper analyzes WMAP 7-year data to confirm the presence of the Galactic microwave haze, improving component separation techniques and modeling the Galactic foreground emission more accurately.

Contribution

It introduces an advanced analysis method using Gibbs sampling to jointly model CMB and Galactic foregrounds, confirming the microwave haze as a distinct emission component.

Findings

The microwave haze is robustly detected around the Galactic center.

Inclusion of Haslam 408MHz data improves foreground modeling.

The haze cannot be explained solely by spectral index variations.

Abstract

We analyse WMAP 7-year temperature data, jointly modeling the cosmic microwave background (CMB) and Galactic foreground emission. We use the Commander code based on Gibbs sampling. Thus, from the WMAP7 data, we derive simultaneously the CMB and Galactic components on scales larger than 1deg with sensitivity improved relative to previous work. We conduct a detailed study of the low-frequency foreground with particular focus on the "microwave haze" emission around the Galactic center. We demonstrate improved performance in quantifying the diffuse galactic emission when Haslam 408MHz data are included together with WMAP7, and the spinning and thermal dust emission is modeled jointly. We also address the question of whether the hypothetical galactic haze can be explained by a spatial variation of the synchrotron spectral index. The excess of emission around the Galactic center appears stable with respect to variations of the foreground model that we study. Our results demonstrate that the new galactic foreground component - the microwave haze - is indeed present.