POINT SOURCES IN THE WILKINSON MICROWAVE ANISOTROPY PROBE SKY MAPS

摘要

We discuss point-source foregrounds for the Wilkinson Microwave Anisotropy Probe (WMAP) experiment. We consider several possible strategies for removing them and we assess how the statistics of the cosmic microwave background (CMB) signal are affected by the residual sources. Assuming a power-law distribution for the point sources, we propose a method aimed at determining the slope of the distribution from the analysis of the moments of the observed maps. The same method allows for a determination of the underlying CMB variance. We conclude that the best strategy for finding point sources is the simultaneous thresholding of the filtered map at all frequencies, with a relatively low threshold. With this strategy, we expect to find 70% (95%) of the sources above 3 (4)σ. Assuming the most conservative case for point-source detection, the recovered slope of the point-source distribution is 2.55 +-0.15, for a fiducial n = 2.5 value. The recovered CMB plus noise map variance is within 0.2% from the real one, with a standard deviation of 0.31%, while cosmic variance contributes 2.2% to the same CMB plus noise map.