Cross-correlation of cosmic voids with thermal Sunyaev–Zel’dovich data

Abstract

ABSTRACT We provide a measurement of the deficit in the Sunyaev–Zel’dovich Compton-y signal towards cosmic voids, by stacking a catalogue of 97 090 voids constructed with BOSS-DR12 data, on the y-maps built on data from the Atacama Cosmology Telescope (ACT) DR4 and the Planck satellite. We detect the void signal with a significance of $7.3 \sigma$ with ACT and $9.7\sigma$ with Planck, obtaining agreements in the associated void radial y-profiles extracted from both maps. The inner-void profile (for angular separations within the void angular radius) is reconstructed with significances of 4.7σ and 6.1σ with ACT and Planck, respectively; we model such profile using a simple model that assumes uniform gas (under)density and temperature, which enables us to place constraints on the product (−δvTe) of the void density contrast (negative) and the electron temperature. The best-fitting values from the two data sets are $(-\delta _{\rm v}T_{\rm e})=(6.5\pm 2.3)\times 10^{5}\, \text{K}$ for ACT and $(8.6 \pm 2.1)\times 10^{5}\, \text{K}$ for Planck [68 per cent confidence level (CL)], which are in good agreement under uncertainty. The data allow us to place lower limits on the expected void electron temperature at $2.7\times 10^5\, \text{K}$ with ACT and $5.1\times 10^5\, \text{K}$ with Planck (95 per cent CL); these results can transform into upper limits for the ratio between the void electron density and the cosmic mean as $n^{\rm v}_{\rm e}/\bar{n}_{\rm e}\leqslant 0.73$ and 0.49 (95 per cent CL), respectively. Our findings prove the feasibility of using thermal Sunyaev–Zel’dovich observations to constrain the gas properties inside cosmic voids, and confirm that voids are under-pressured regions compared to their surroundings.