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

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 $7.3\ddot{I}ƒ$ with ACT and $9.7\ddot{I}ƒ$ 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 $4.7\ddot{I}ƒ$ and $6.1\ddot{I}ƒ$ 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 $(-\hat{I}{´}_{\mathrm{v}}{T}_{\mathrm{e}})$ of the void density contrast (negative) and the electron temperature. The best-fit values from the two data sets are $(-\hat{I}{´}_{\mathrm{v}}{T}_{\mathrm{e}})=(6.5\pm 2.3)\times 10^5\text{K}$ for ACT and $(8.6\pm 2.1)\times 10^5\text{K}$ for Planck ($68\%$ C.L.), 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 ($95\%$ C.L.); these results can transform into upper limits for the ratio between the void electron density and the cosmic mean as $n_{\mathrm{e}}^{\mathrm{v}}/{\bar{n}}_{\mathrm{e}}⩽0.73$ and $0.49$ ($95\%$ C.L.), respectively. Our findings prove the feasibility of using tSZ observations to constrain the gas properties inside cosmic voids, and confirm that voids are under-pressured regions compared to their surroundings.

9 pages, 7 figures