The DES view of the Eridanus supervoid and the CMB Cold Spot

TL;DR

This study investigates the Eridanus supervoid's role in the CMB Cold Spot, confirming its significant under-density and exploring its lensing signal, which shows some deviations from standard cosmological expectations.

Contribution

The paper provides the first confirmation of the Eridanus supervoid as a major under-density in the Cold Spot region using multiple datasets and examines its lensing properties in relation to $ m extLambda$CDM predictions.

Findings

Eridanus supervoid is a significant under-density at $z<0.2$ in the Cold Spot direction.

Lensing signal amplitude from the supervoid is about 30% lower than $ m extLambda$CDM expectations.

No significant anomalies found, but results suggest potential deviations worth further investigation.

Abstract

The Cold Spot is a puzzling large-scale feature in the Cosmic Microwave Background temperature maps and its origin has been subject to active debate. As an important foreground structure at low redshift, the Eridanus supervoid was recently detected, but it was subsequently determined that, assuming the standard $\Lambda$CDM model, only about 10-20$\%$ of the observed temperature depression can be accounted for via its Integrated Sachs-Wolfe imprint. However, $R\gtrsim100~h^{-1}\mathrm{Mpc}$ supervoids elsewhere in the sky have shown ISW imprints $A_{\mathrm{ISW}}\approx5.2\pm1.6$ times stronger than expected from $\Lambda$CDM ($A_{\mathrm{ISW}}=1$), which warrants further inspection. Using the Year-3 redMaGiC catalogue of luminous red galaxies from the Dark Energy Survey, here we confirm the detection of the Eridanus supervoid as a significant under-density in the Cold Spot's direction at $z<0.2$. We also show, with $\mathrm{S/N}\gtrsim5$ significance, that the Eridanus supervoid appears as the most prominent large-scale under-density in the dark matter mass maps that we reconstructed from DES Year-3 gravitational lensing data. While we report no significant anomalies, an interesting aspect is that the amplitude of the lensing signal from the Eridanus supervoid at the Cold Spot centre is about $30\%$ lower than expected from similar peaks found in N-body simulations based on the standard $\Lambda$CDM model with parameters $\Omega_{\rm m} = 0.279$ and $\sigma_8 = 0.82$. Overall, our results confirm the causal relation between these individually rare structures in the cosmic web and in the CMB, motivating more detailed future surveys in the Cold Spot region.