A shock near the virial radius of the Perseus Cluster

¹ SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
e-mail: Z.Zhu@sron.nl
² Leiden Observatory, Leiden University, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands
³ Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, 277-8583 Kashiwa, Chiba, Japan
⁴ Trayport, Lemböckgasse 49/1A/5.OG, 1230 Vienna, Austria
⁵ Department of Physics, Stanford University, 382 Via Pueblo Mall, 94305 Stanford, CA, USA
⁶ Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, 94305 Stanford, CA, USA
⁷ SLAC National Accelerator Laboratory, 2575 Sand Hill Road, 94025 Menlo Park, CA, USA
⁸ Department of Theoretical Physics and Astrophysics, Masaryk University, Kotlárská 2, 61137 Brno, Czech Republic

Received: 26 February 2021
Accepted: 30 June 2021

Abstract

Context. Previous X-ray studies of the Perseus Cluster, consisting of 85 Suzaku pointings along eight azimuthal directions, revealed a particularly steep decrease in the projected temperature profile near the virial radius (∼r₂₀₀) towards the northwest (NW).

Aims. To further explore this shock candidate, another 4 Suzaku observations on the NW edge of the Perseus Cluster have been obtained. These deeper data were designed to provide the best possible control of systematic uncertainties in the spectral analysis.

Methods. Using the combined Suzaku observations, we have carefully investigated this interesting region by analyzing the spectra of various annuli and extracting projected thermodynamic profiles.

Results. We find that the projected temperature profile shows a break near r₂₀₀, indicating a shock with ℳ = 1.9 ± 0.3. Corresponding discontinuities are also found in the projected emission measure and the density profiles at the same location. This evidence of a shock front so far away from the cluster center is unprecedented, and may provide a first insight into the properties of large-scale virial shocks which shape the process of galaxy cluster growth.