A new technique to extract point sources from CMB maps
E. P. G. Ramos, R. Vio, P. Andreani
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 with steep and inverted spectra. We apply this method to three Southern Hemisphere sky regions – each with an area of 400 deg2 – 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.
methods: data analysis – cosmic microwave background - methods: statistical - radio continuum: galaxies
Astronomy & Astrophysics
Volume 528, Number of pages A75_1