A shock front at the radio relic of Abell 2744

• DOI: 10.1093/mnras/stw1435
• Publication Date: 2016-06-16T21:19:41Z
• Authors: D. Eckert; M. Jauzac; F. Vazza; M. S. Owers; J.-P. Kneib; C. Tchernin; H. Intema; K. Knowles
• Keywords: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO); FOS: Physical sciences; 530; 01 natural sciences; 520; galaxies: clusters: individual: A2744; X-rays: galaxies: clusters; 0103 physical sciences; Galaxies: clusters: individual: A2744; X-rays: galaxies: clusters; Astronomy and Astrophysics; Space and Planetary Science; Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Cosmology and Nongalactic Astrophysics

6 pages, 4 figures, MNRAS in press<br/>Radio relics are Mpc-scale diffuse radio sources at the peripheries of galaxy clusters which are thought to trace outgoing merger shocks. We present XMM-Newton and Suzaku observations of the galaxy cluster Abell 2744 (z=0.306), which reveal the presence of a shock front 1.5 Mpc East of the cluster core. The surface-brightness jump coincides with the position of a known radio relic. Although the surface-brightness jump indicates a weak shock with a Mach number $\mathcal{M}=1.7_{-0.3}^{+0.5}$, the plasma in the post-shock region has been heated to a very high temperature ($\sim13$ keV) by the passage of the shock wave. The low acceleration efficiency expected from such a weak shock suggests that mildly relativistic electrons have been re-accelerated by the passage of the shock front.<br/>