Point source power in three-year Wilkinson Microwave Anisotropy Probe data

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  • 21 June 2006
Abstract
Using a set of multifrequency cross-spectra computed from the three year WMAP sky maps, we fit for the unresolved point source contribution. For a white noise power spectrum, we find a Q-band amplitude of A = 0.011 +/- 0.001 muK^2 sr (antenna temperature), significantly smaller than the value of 0.017 +/- 0.002 muK^2 sr used to correct the spectra in the WMAP release. Modifying the point source correction in this way largely resolves the discrepancy Eriksen et al. (2006) found between the WMAP V- and W-band power spectra. Correcting the co-added WMAP spectrum for both the low-l power excess due to residual foregrounds and the high-l power deficit due to over-subtracted point sources, we find that the net effect in terms of cosmological parameters is a ~ 0.7 sigma shift in n_s to larger values: For the combination of WMAP, BOOMERanG and Acbar data, we find n_s = 0.969 +/- 0.016, lowering the significance of n_s not equal to 1 from ~ 2.7 sigma to ~ 2.0 sigma.

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