Residual foreground contamination in the WMAP data

Abstract

We have studied whether there is any residual foreground contamination in the foreground reduced WMAP-7 data for the differential assemblies (DAs) Q, V and W. We have calculated the correlation between the foreground map, from which long wavelength correlations have been subtracted, and the foreground reduced map for each DA. We have found positive correlations for all the channels. The statistical significance of the resulting values has been tested by comparing with correlations between the cleaned CMB maps and 1000 simulated Gaussian maps to which instrumental effects have been added. We have found high statistical significance of the observed correlations, implying the presence of residual contamination in the cleaned data, and found that, for Q and V channels, a large fraction of the contamination comes from pixels, where the foreground maps have positive values larger than three times its rms value, which shows the presence of unresolved point sources that contribute significantly to the contamination.