The One-dimensional Fourier Representation and Large Angular Scale Foreground Contamination in the 3-year Wilkinson Microwave Anisotropy Probe data
نویسندگان
چکیده
We employ the one-dimensional Fourier representation (1DFR) to analyze the 3-year WMAP de-biased internal linear combination (DILC) map and its possible contamination by galactic foregrounds. The 1DFR is a representation of the spherical harmonic coefficients for each l–mode using an inverse Fourier transform into onedimensional curves. Based on the a priori assumption that the CMB signal should be statistically independent of, and consequently have no significant correlation with, any foregrounds, we cross-correlate the 1DFR curves of 2 ≤ l ≤ 10 modes, which are claimed by the WMAP team to be free of contamination and suitable for whole sky analysis. We find that 8 out of the 9 modes are negatively cross correlated with the foreground maps, an event which has a probability of only 9/512 ≃ 0.0176 for uncorrelated signals. Furthermore, the local extrema of the 1DFR curves between the DILC and those of the foregrounds for l = 2 and 6 are correlated with significance level below 0.04. We also discuss the minimum variance optimization method and use the properties of the measured cross-correlation to estimate the possible level of contamination present in the DILC map. PACS numbers: 98.80.-k, 95.85.Bh, 98.70.Vc, 95.75.-z
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