The CMB cold spot under the lens: ruling out a supervoid interpretation

The Cosmic Microwave Background (CMB) anisotropies are thought to be statis-tically isotropic and Gaussian. However, several anomalies are observed, including the CMB Cold Spot, an unexpected cold ti 10 & DEG; region with p-value $ 0.01 in standard ACDM. One of the proposed origins of the Cold Spot is an unusually large void on the line of sight, that would generate a cold region through the combination of integrated Sachs-Wolfe and Rees-Sciama effects. In the past decade extensive searches were conducted in large scale structure surveys, both in optical and infrared, in the same area for z & LE; 1 and did find evidence of large voids, but of depth and size able to account for only a fraction of the anomaly. Here we analyze the lensing signal in the Planck CMB data and rule out the hypothesis that the Cold Spot could be due to a large void located anywhere between us and the surface of last scattering. In particular, computing the evidence ratio we find that a model with a large void is disfavored compared to ACDM, with odds 1 : 13 (1 : 20) for SMICA (NILC) maps, compared to the original odds 56 : 1 (21 : 1) using temperature data alone.

Automated summary

The Cosmic Microwave Background (CMB) anisotropies are expected to be uniform and follow a normal distribution. However, there are anomalies observed, such as the CMB Cold Spot, which is a colder than expected region with a p-value of 0.01 in standard ACDM cosmology. One possible explanation is the presence of a large void on the line of sight that causes a cold region through integrated Sachs-Wolfe and Rees-Sciama effects. Extensive searches have been conducted in the past decade, but only partially account for the anomaly. In this study, the lensing signal in the Planck CMB data is analyzed and the hypothesis of a large void causing the Cold Spot is ruled out.