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

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 (cid:2) CDM model, only about 10–20 per cent of the observed temperature depression can be accounted for via its Integrated Sachs–Wolfe imprint. Ho we ver, R (cid:2) 100 h − 1 Mpc supervoids elsewhere in the sk y hav e shown ISW imprints A ISW ≈ 5.2 ± 1.6 times stronger than e xpected from (cid:2) CDM ( A ISW = 1), which warrants further inspection. Using the Year-3 redMaGiC catalogue of luminous red galaxies from the Dark Energy Surv e y, here we confirm the detection of the Eridanus supervoid as a significant underdensity in the Cold Spot’s direction at z < 0.2. We also show, with S/N (cid:2) 5 significance, that the Eridanus supervoid appears as the most prominent large-scale underdensity 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 per cent lower than expected from similar peaks found in N-body simulations based on the standard (cid:2) CDM model with parameters (cid:3) m = 0.279 and σ 8 = 0.82. Overall, our results confirm the causal relation between these individually rare structures in the cosmic web and in the CMB, moti v ating more detailed future surv e ys in the Cold Spot region.