X-ray study of the double radio relic Abell 3376 with Suzaku

¹ SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
e-mail: i.urdampilleta@sron.nl
² Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
³ MTA-Eötvös University Lendület Hot Universe Research Group, Pázmány Péter sétány 1/A, Budapest, 1117 Hungary
⁴ Institute of Physics, Eötvös University, Pázmány Péter sétány 1/A, Budapest, 1117 Hungary
⁵ Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397 Japan
⁶ Department of Earth and Planetary Science, The University of Tokyo, Tokyo, 113-0033 Japan
⁷ Research Center for the Early Universe, School of Science, The University of Tokyo, Tokyo, 113-0033 Japan

Received: 19 December 2017
Accepted: 20 June 2018

Abstract

We present an X-ray spectral analysis of the nearby double radio relic merging cluster Abell 3376 (z = 0.046), observed with the Suzaku XIS instrument. These deep (∼360 ks) observations cover the entire double relic region in the outskirts of the cluster. These diffuse radio structures are amongst the largest and arc-shaped relics observed in combination with large-scale X-ray shocks in a merging cluster. We confirm the presence of a stronger shock (ℳ_W = 2.8 ± 0.4) in the western direction at r ∼ 26′, derived from a temperature and surface brightness discontinuity across the radio relic. In the east, we detect a weaker shock (ℳ_E = 1.5 ± 0.1) at r ∼ 8′, possibly associated with the “notch” of the eastern relic, and a cold front at r ∼ 3′. Based on the shock speed calculated from the Mach numbers, we estimate that the dynamical age of the shock front is ∼0.6 Gyr after core passage, indicating that Abell 3376 is still an evolving merging cluster and that the merger is taking place close to the plane of the sky. These results are consistent with simulations and optical and weak lensing studies from the literature.