We cross-correlate the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data and the diffuse gammaray intensity maps from the Energetic Gamma-Ray Experiment Telescope (EGRET) using spherical-wavelet approaches. Correlations at the 99.7% significance level have been detected, at scales around 15° in the WMAP foreground-cleaned W-band and Q-band maps, based on data from regions that are outside the most conservative WMAP foreground mask; no significant correlation is found with the Tegmark cleaned map. The detected correlation is most likely of Galactic origin and thus can help probe the origins of possible Galactic foreground residuals and ultimately remove them from measured microwave sky maps.
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