Too few spots in the cosmic microwave background

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 cosmic microwave background (CMB) region, i.e., outside the foreground-contaminated parts excluded by the KQ75 mask. Even simulated maps created from the original WMAP-5 estimated multipoles contain more spots than visible in the measured CMB maps. A strong suppression of the lowest multipoles would lead to better agreement. The lack of spots is reflected in a low mean temperature fluctuation on scales of several degrees (4 to 8), which is only shared by less than 1% (0.16%-0.62%) of Gaussian LCDM simulations. After removing the quadrupole, the probabilities change to 2.5%-8.0%. This shows the importance of the anomalously low quadrupole for the statistical significance of the missing spots. We also analyze a possible violation of Gaussianity or statistical isotropy (spots are distributed differently outside and inside the masked region).

12 pages; changes in the abstract, extended discussion of the quadrupole and the significances, minor clarifications, one added figure (behavior of typical simulations), one added reference

References in corpus (11)

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• A comprehensive overview of the Cold Spot
• Anomalous variance in the WMAP data and Galactic Foreground residuals
• Perceiving the equation of state of Dark Energy while living in a Cold Spot
• Uncertainty on w from large-scale structure
• Non-gaussianity in the foreground-reduced CMB maps
• Mass freezing in growing neutrino quintessence
• Extreme value statistics of smooth random Gaussian fields
• Searching for planar signatures in WMAP
• Correlation of supernova redshifts with temperature fluctuations of the Cosmic Microwave Background
• An overview of the current status of CMB observations
• Non-Gaussianity in the HILC foreground-reduced three-year WMAP CMB map
• A Study of Gaussianity in CMB band maps
• Non-Gaussian Distribution and Clustering of Hot and Cold Pixels in the WMAP Five-Year Sky