FOREGROUND ANALYSIS FROM THE 1-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP) DATA

We present a detailed analysis on the phases of the WMAP foregrounds (synchrotron, free–free and dust emission) of the WMAP K–W bands in order to estimate the significance of the variation of the spectral indices at different components. We first extract the spectral-index varying signals by assuming that the invariant part among different frequency bands have 100% cross-correlation of phases. We then use the minimization of variance, which is normally used for extracting the CMB signals, to extract the frequency independent signals. Such a common signal in each foreground component could play a significant role for any kind of component separation methods, because the methods cannot discriminate frequency independent foregrounds and CMB.