# The part and the whole: voids, supervoids, and their ISW imprint

## TL;DR

This study investigates the ISW imprint of supervoids in the cosmic web, revealing an excess signal in real data compared to simulations, which may relate to the CMB Cold Spot and challenge standard cosmological models.

## Contribution

It demonstrates how supervoid definitions affect ISW signals, introduces a new profile shape for supervoids, and finds a significant excess ISW signal in BOSS data compared to LambdaCDM predictions.

## Key findings

- Supervoids show a distinctive ISW imprint with cold centers and hot rings.
- BOSS supervoids exhibit a more compact profile than simulations, requiring size rescaling.
- Detected excess ISW signal with amplitude A_{ISW} D 9 at 2.5C3 significance, hinting at new physics.

## Abstract

The integrated Sachs-Wolfe imprint of extreme structures in the cosmic web probes the dynamical nature of dark energy. Looking through typical cosmic voids, no anomalous signal has been reported. On the contrary, supervoids, associated with large-scale fluctuations in the gravitational potential, have shown potentially disturbing excess signals. In this study, we used the Jubilee ISW simulation to demonstrate how the stacked signal depends on the void definition. We found that large underdensities, with at least $\approx5$ merged sub-voids, show a peculiar ISW imprint shape with central cold spots and surrounding hot rings, offering a natural way to define supervoids in the cosmic web. We then inspected the real-world BOSS DR12 data using the simulated imprints as templates. The imprinted profile of BOSS supervoids appears to be more compact than in simulations, requiring an extra $\alpha \approx 0.7$ re-scaling of filter sizes. The data reveals an excess ISW-like signal with $A_{\rm ISW}\approx9$ amplitude at the $\approx2.5\sigma$ significance level, unlike previous studies that used isolated voids and reported good consistency with $A_{\rm ISW}=1$. The tension with the Jubilee-based $\Lambda$CDM predictions is $\sim 2\sigma$, in consistency with independent analyses of supervoids in Dark Energy Survey data. We show that such a very large enhancement of the $A_{\rm ISW}$ parameter hints at a possible causal relation between the CMB Cold Spot and the Eridanus supervoid. The origin of these findings remains unclear.