Too few spots in the Cosmic Microwave Background

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Abstract
We investigate the abundance of large-scale hot and cold spots in the WMAP-5 temperature maps and find considerable discrepancies compared to Gaussian simulations based on the LCDM best-fit model. Too few spots are present in the reliably observed CMB region, i.e. outside the foreground-contaminated parts excluded by the KQ75 mask. This can only partially be explained by the well-known quadrupole anomaly. Even simulated maps created from the original WMAP-5 estimated multipoles contain more spots than visible in the measured CMB maps. We analyze two possible origins of the discrepancies: statistical anisotropy violating Gaussianity (spots are distributed differently outside and inside the masked region) or an even more drastic lack of power than implied by the low quadrupole. This lack of power on scales of several degrees, quantified by the mean temperature fluctuation, is only shared by less than 1% of Gaussian LCDM simulations. We show that the discrepancies disappear when the lowest multipoles are strongly suppressed.

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