Supervoid Origin of the Cold Spot in the Cosmic Microwave Background

TL;DR

This paper investigates whether a large supervoid could explain the Cosmic Microwave Background Cold Spot by analyzing galaxy distribution data, finding evidence for a supervoid that could account for the anomaly.

Contribution

It provides the first detailed tomographic analysis linking a supervoid to the Cold Spot, suggesting a plausible supervoid origin within the standard cosmological model.

Findings

Identified a supervoid with radius ~192 Mpc/h at z=0.22

Supervoid's density contrast is approximately -0.13

Supervoid fluctuation is about 3.5 sigma in ΛCDM model

Abstract

We use a WISE-2MASS-Pan-STARRS1 galaxy catalog to search for a supervoid in the direction of the Cosmic Microwave Background Cold Spot. We obtain photometric redshifts using our multicolor data set to create a tomographic map of the galaxy distribution. The radial density profile centred on the Cold Spot shows a large low density region, extending over 10's of degrees. Motivated by previous Cosmic Microwave Background results, we test for underdensities within two angular radii, $5^\circ$, and $15^\circ$. Our data, combined with an earlier measurement by Granett et al 2010, are consistent with a large $R_{\rm void}=(192 \pm 15)h^{-1} Mpc $ $(2\sigma)$ supervoid with $\delta \simeq -0.13 \pm 0.03$ centered at $z=0.22\pm0.01$. Such a supervoid, constituting a $\sim3.5 \sigma$ fluctuation in the $\Lambda CDM$ model, is a plausible cause for the Cold Spot.