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

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 7.3σ with ACT and 9.7σ 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 (−δvTe)=(6.5±2.3)×105K for ACT and (8.6±2.1)×105K 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 2.7×105K with ACT and 5.1×105K 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 nve/n¯e⩽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.