Imprint of DES super-structures on the Cosmic Microwave Background

TL;DR

This study investigates the imprint of large cosmic structures on the CMB using DES data, finding signals slightly above standard cosmological model expectations, with implications for understanding the ISW effect.

Contribution

It provides an independent analysis of super-structure imprints on the CMB with new data, methods, and a comparison to prior findings, highlighting potential deviations from ΛCDM.

Findings

Detected a cold imprint of voids (~-5 μK) and hot of superclusters (~5 μK) with marginal significance.

Observed signals are slightly higher than ΛCDM predictions, up to about 2σ.

Results are consistent with previous SDSS-based measurements, suggesting possible anomalies or new physics.

Abstract

Small temperature anisotropies in the Cosmic Microwave Background can be sourced by density perturbations via the late-time integrated Sachs-Wolfe effect. Large voids and superclusters are excellent environments to make a localized measurement of this tiny imprint. In some cases excess signals have been reported. We probed these claims with an independent data set, using the first year data of the Dark Energy Survey in a different footprint, and using a different super-structure finding strategy. We identified 52 large voids and 102 superclusters at redshifts $0.2 < z < 0.65$. We used the Jubilee simulation to a priori evaluate the optimal ISW measurement configuration for our compensated top-hat filtering technique, and then performed a stacking measurement of the CMB temperature field based on the DES data. For optimal configurations, we detected a cumulative cold imprint of voids with $\Delta T_{f} \approx -5.0\pm3.7~\mu K$ and a hot imprint of superclusters $\Delta T_{f} \approx 5.1\pm3.2~\mu K$ ; this is $\sim1.2\sigma$ higher than the expected $|\Delta T_{f}| \approx 0.6~\mu K$ imprint of such super-structures in $\Lambda$CDM. If we instead use an a posteriori selected filter size ($R/R_{v}=0.6$), we can find a temperature decrement as large as $\Delta T_{f} \approx -9.8\pm4.7~\mu K$ for voids, which is $\sim2\sigma$ above $\Lambda$CDM expectations and is comparable to previous measurements made using SDSS super-structure data.