To the center of cold spot with Planck

TL;DR

This paper investigates the cold spot in the CMB using Planck data, revealing a shell-like non-Gaussian structure that supports the hypothesis of a cosmic void, and introduces a method for detecting voids without redshift data.

Contribution

The study introduces a new K-map analysis revealing a shell structure in the cold spot, supporting its void nature and offering a method to trace voids without redshift surveys.

Findings

Shell structure in the cold spot detected at 100 GHz

Non-Gaussianity of the shell at 4σ confidence level

Method can trace voids without redshift data

Abstract

The structure of the cold spot, of a non-Gaussian anomaly in the cosmic microwave background (CMB) sky first detected by Vielva et al. is studied using the data by Planck satellite. The obtained map of the degree of stochasticity (K-map) of CMB for the cold spot, reveals, most clearly in 100 GHz band, a shell-type structure with a center coinciding with the minima of the temperature distribution. The shell structure is non-Gaussian at a 4\sigma confidence level. Such behavior of the K-map supports the void nature of the cold spot. The applied method can be used for tracing voids that have no signatures in redshift surveys.