paper

Spectral age modelling of the `Sausage' cluster radio relic

arXiv:1409.1579 · doi:10.1093/mnras/stu1839

Abstract

CIZA J2242.8+5301 is a post-core passage, binary merging cluster that hosts a large, thin, arc-like radio relic, nicknamed the `Sausage', tracing a relatively strong shock front. We perform spatially-resolved spectral fitting to the available radio data for this radio relic, using a variety of spectral ageing models, with the aim of finding a consistent set of parameters for the shock and radio plasma. We determine an injection index of for the relic plasma, significantly steeper than was found before. Standard particle acceleration at the shock front implies a Mach number , which now matches X-ray measurements. The shock advance speed is km s, which places the core passage of the two subclusters Gyr ago. We find a systematic spectral age increase from at the northern side of the relic up to Myr at kpc into the downstream area, assuming a nT magnetic field. Under the assumption of freely-ageing electrons after acceleration by the `Sausage' shock, the spectral ages are hard to reconcile with the shock speed derived from X-ray and radio observations. Re-acceleration or unusually efficient transport of particle in the downstream area and line-of-sight mixing could help explain the systematically low spectral ages.

arXiv commentAccepted for publication in MNRAS. 10 pages, 6 figures, 2 tables

References in corpus (41)

Cited by in corpus (48)