Component separation in CMB observations

TL;DR

This paper presents a method to extract a clean CMB map and foreground emissions from WMAP data using a spherical needlet-based internal linear combination, enabling better analysis of galactic and cluster signals.

Contribution

It introduces a localized needlet-based internal linear combination technique for improved component separation in CMB data analysis.

Findings

Successful extraction of a full-sky CMB map with high accuracy.

Detection of the Sunyaev-Zel'dovich effect through stacking analysis of galaxy clusters.

Measurement of SZ flux scaling with cluster mass and X-ray luminosity.

Abstract

In these proceedings, we discuss the extraction, in WMAP 5 year data, of a clean CMB map, of foreground emission (dominated by emission of the interstellar medium of our galaxy), and of the tiny signal from Sunyaev Zel'dovich effect in the direction of known galaxy clusters. The implementation of an Internal Linear Combination method locally in both pixel and harmonic space, with the use of a decomposition of WMAP maps onto a frame of spherical needlets, permits to extract a full sky CMB map, with good accuracy even in regions close to the galactic plane. Proper subtraction of this estimated CMB from WMAP original observations provides us with CMB-free foreground maps, which can be used for the analysis of the emission of the galactic interstellar medium and for detecting and measuring emissions from compact sources. Finally, while the Sunyaev-Zel'dovich cannot be detected for individual clusters in WMAP data, due to lack of spatial resolution and sensitivity, a stacking analysis of tentative detections towards a number of known ROSAT clusters permits to detect the SZ effect in WMAP data and measure how the SZ flux scales with cluster mass and X-ray luminosity.