Point-Source Power in 3 Year Wilkinson Microwave Anisotropy Probe Data

Using a set of multifrequency cross spectra computed from the 3 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 that Eriksen et al. 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 a suboptimal likelihood approximation--also reported by Eriksen et al.--and the high-l power deficit due to oversubtracted point sources--presented in this Letter--we find that the net effect in terms of cosmological parameters is an \~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.

K. M. Huffenberger, H. K. Eriksen, F. K. Hansen · 2006