CMB Cold Spot in the Planck Light

The Cold Spot, with an unusually cold region surrounded by a hot ring, is a statistically significant anomaly in the cosmic microwave background (CMB) sky. In this work we assess whether different sets of multiple subvoids based on the 2dF-VST ATLAS Cold Spot galaxy redshift survey or a collapsing cosmic texture could have produced such an anomaly through a simultaneous search for their gravitational redshift and lensing signatures on the Planck CMB temperature anisotropies. We use patches with radii R = 10 degrees and R = 20 degrees to account for the inner cold region as well as the outer hot ring. As the void model, we explore two sets of Lambda LTB templates characterized by different values of the model's free parameters, and a top-hat void template. We detect higher than expected gravitational redshift amplitudes for the first two sets, A(rs) = 5.4 +/- 1.4 and A(rs) = 14.4 +/- 3.8, and lower than expected for the top-hat model, A(rs) = 0.3 +/- 0.1. The amplitudes for the lensing imprint are consistent with zero for all these subvoid models. The estimated amplitude for the texture imprint from the gravitational redshift measurement implies the energy scale of the texture, parameterized by epsilon, to be epsilon = (7.6 +/- 2.0) x 10(-5), with no detection of the lensing trace. We note that the deviation of the subvoid amplitudes from unity and the inability of the texture and some of the void profiles to reproduce the hot ring indicate theoretical insufficiencies, either in the construction of the model or in the assumed gravitational and cosmological framework leading to the imprints for the structures.

Automated summary

The study investigates the anomalous Cold Spot in the cosmic microwave background sky, evaluating whether different sets of subvoids could have produced this anomaly. It was found that some models showed gravitational redshift amplitudes higher than expected, while the lensing imprint amplitudes were consistent with zero.