Cleaned 3 YearWilkinson Microwave Anistropy ProbeCosmic Microwave Background Map: Magnitude of the Quadrupole and Alignment of Large‐Scale Modes

We have produced a cleaned CMB temperature fluctuation map of the Wilkinson Microwave Anisotropy Probe ( WMAP ) 3 year data using an improved internal linear combination (ILC) method as a Galactic foreground subtraction technique. We divide the whole sky into hundreds of pixel groups with similar foreground spectral indices over a range of WMAP frequencies, apply the ILC for each group, and obtain a CMB map with foreground emission effectively reduced. With the resulting ILC map, we have investigated the known anomalies in CMB maps at large scales, namely, the low quadrupole ( l = 2) power, and the strong alignment and planarity of the quadrupole and the octopole ( l = 3). Our estimates are consistent with the previous measurements. The quadrupole and the octopole powers measured from our ILC map are δ T = 276 μK 2 and δ T = 952 μK 2 , respectively. The 68% confidence limits are estimated from the ILC simulations and include the cosmic variance. The measured quadrupole power is lower than the value expected in the concordance ΛCDM model (1250 μK 2 ), in which the probability of finding a quadrupole power lower than the measured value is p = 5.7%. We have confirmed that the quadrupole and the octopole are strongly aligned with angle θ 23 = 11.8 ° and are planar with high planarity parameters t = 0.98 ± 0.02 for l = 2 and t = 0.91 for l = 3. The observed angular separation θ 23 is marginally significant with p = 4.3%. However, the observed planarity is not statistically significant. The probability of observing such a planarity as high as the measured t -values is over 18%. The ILC simulations show that the residual foreground emission in the ILC map does not affect the estimated values significantly.