Discovery of a radio relic in the low mass, merging galaxy cluster PLCK G200.9-28.2

作者：Kale Ruta^*; Wik Daniel R^*; Giacintucci Simona; Venturi Tiziana; Brunetti Gianfranco; Cassano Rossella; Dallacasa Daniele; de Gasperin Francesco

来源：Monthly Notices of the Royal Astronomical Society, 2017, 472(1): 940-948.

DOI：10.1093/mnras/stx2031

• radiation mechanisms: non-thermal
• shock waves
• galaxies: clusters: individual: PLCKG200.9-28.2
• galaxies: clusters: intracluster medium
• radio continuum: general
• X-rays: galaxies: clusters

Radio relics at the peripheries of galaxy clusters are tracers of the elusive cluster merger shocks. We report the discovery of a single radio relic in the galaxy cluster PLCK G200.9-28.2 (z = 0.22, M-500 = 2.7 +/- 0.2 x 10(14)M(circle dot)) using the Giant Metrewave Radio Telescope at 235 and 610 MHz and the Karl G. Jansky Very Large Array at 1500 MHz. The relic has a size of similar to 1 x 0.28 Mpc, an arc-like morphology and is located at 0.9 Mpc from the X-ray brightness peak in the cluster. The integrated spectral index of the relic is 1.21 +/- 0.15. The spectral index map between 235 and 610MHz shows steepening from the outer to the inner edge of the relic in line with the expectation from a cluster merger shock. Under the assumption of diffusive shock acceleration, the radio spectral index implies a Mach number of 3.3 +/- 1.8 for the shock. The analysis of archival XMM-Newton data shows that PLCK G200.9-28.2 consists of a northern brighter sub-cluster, and a southern sub-cluster in a state of merger. This cluster has the lowest mass amongst the clusters hosting single radio relics. The position of the Planck Sunyaev-Ze'ldovich effect in this cluster is offset by 700 kpc from the X-ray peak in the direction of the radio relic, suggests a physical origin for the offset. Such large offsets in low mass clusters can be a useful tool to select disturbed clusters and to study the state of merger.

• 出版日期2017-11