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).
Keywords
Cite
@article{arxiv.0905.3324,
title = {Too few spots in the cosmic microwave background},
author = {Youness Ayaita and Maik Weber and Christof Wetterich},
journal= {arXiv preprint arXiv:0905.3324},
year = {2010}
}
Comments
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