2018MNRAS.475.1777K

The integrated Sachs-Wolfe (ISW) 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 ≃5 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 Baryon Oscillations Spectroscopic Survey data release 12 (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 α ≃ 0.7 re-scaling of filter sizes. The data reveal an excess ISW-like signal with A_ISW ≃ 9 amplitude at the ≃2.5σ significance level, unlike previous studies that used isolated voids and reported good consistency with A_ISW = 1. The tension with the Jubilee-based Λ cold dark matter predictions is >=2σ, in consistency with independent analyses of supervoids in Dark Energy Survey data. We show that such a very large enhancement of the A_ISW parameter hints at a possible causal relation between the cosmic microwave background Cold Spot and the Eridanus supervoid. The origin of these findings remains unclear.