Direct detection of the kinetic Sunyaev-Zel’dovich effect in galaxy clusters

¹ Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, Bâtiment 121, 91405 Orsay, France
e-mail: hideki.tanimura@ias.u-psud.fr
² Department of Natural Sciences, Open University of Israel, 1 University Road, PO Box 808, Ra’anana 4353701, Israel
³ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
⁴ Department of Physics, The Technion, Haifa 32000, Israel

Received: 4 July 2020
Accepted: 15 November 2020

Abstract

We report the direct detection of the kinetic Sunyaev-Zel’dovich (kSZ) effect in galaxy clusters with a 3.5σ significance level. The measurement was performed by stacking the Planck map at 217 GHz at the positions of galaxy clusters from the Wen-Han-Liu (WHL) catalog. To avoid the cancelation of positive and negative kSZ signals, we used the large-scale distribution of the Sloan Digital Sky Survey (SDSS) galaxies to estimate the peculiar velocities of the galaxy clusters along the line of sight and incorporated the sign in the velocity-weighted stacking of the kSZ signals. Using this technique, we were able to measure the kSZ signal around galaxy clusters beyond 3 × R₅₀₀. Assuming a standard β-model, we also found that the gas fraction within R₅₀₀ is f_gas, 500 = 0.12 ± 0.04 for the clusters with the mass of M₅₀₀ ∼ 1.0 × 10¹⁴ h⁻¹ M_⊙. We compared this result to predictions from the Magneticum cosmological hydrodynamic simulations as well as other kSZ and X-ray measurements, most of which show a lower gas fraction than the universal baryon fraction for the same mass of clusters. Our value is statistically consistent with results from the measurements and simulations and also with the universal value within our measurement uncertainty.