Detection of new point-sources in WMAP Cosmic Microwave Background (CMB) maps at high Galactic latitude. A new technique to extract point sources from CMB maps

TL;DR

This paper introduces a simple, robust weighted matched filter technique for detecting point sources in WMAP CMB maps, successfully identifying new sources and improving source extraction in microwave sky surveys.

Contribution

A new, easy-to-use weighted matched filter method for point-source detection in CMB maps, demonstrating improved detection of previously unlisted sources in WMAP data.

Findings

Identified seven new point sources in WMAP maps.

The WMF method is more robust and effective for sources with non-zero spectral slopes.

Compared results with existing WMAP catalogs and discussed source properties.

Abstract

In experimental microwave maps, point-sources can strongly affect the estimation of the power-spectrum and/or the test of Gaussianity of the Cosmic Microwave Background (CMB) component. As a consequence, their removal from the sky maps represents a critical step in the analysis of the CMB data. Before removing a source, however, it is necessary to detect it and source extraction consists of a delicate preliminary operation. In the literature, various techniques have been presented to detect point-sources in the sky maps. The most sophisticated ones exploit the multi-frequency nature of the observations that is typical of the CMB experiments. These techniques have "optimal" theoretical properties and, at least in principle, are capable of remarkable performances. Actually, they are rather difficult to use and this deteriorates the quality of the obtainable results. In this paper, we present a new technique, the "weighted matched filter" (WMF), that is quite simple to use and hence more robust in practical applications. Such technique shows particular efficiency in the detection of sources whose spectra have a slope different from zero. We apply this method to three Southern Hemisphere sky regions - each with an area of 400 square degrees - of the seven years Wilkinson Microwave Anisotropy Probe (WMAP) maps and compare the resulting sources with those of the two seven-year WMAP point-sources catalogues. In these selected regions we find seven additional sources not previously listed in WMAP catalogues and discuss their most likely identification and spectral properties.