Nonthermal hard X-ray excess in the Coma cluster: Resolving the discrepancy between the results of different PDS data analyses

Nov, 2006
12 pages
Published in:
  • Astrophys.J.Lett. 654 (2006) L9-L12
e-Print:

Citations per year

2007201120152019202302468
Abstract: (arXiv)
The detection of a nonthermal excess in the Coma cluster spectrum by two BeppoSAX observations analyzed with the XAS package (Fusco-Femiano et al.) has been disavowed by an analysis (Rossetti & Molendi) performed with a different software package (SAXDAS) for the extraction of the spectrum. To resolve this discrepancy we reanalyze the PDS data considering the same software used by Rossetti & Molendi. A correct selection of the data and the exclusion of contaminating sources in the background determination show that also the SAXDAS analysis reports a nonthermal excess with respect to the thermal emission at about the same confidence level of that obtained with the XAS package (~4.8sigma). Besides, we report the lack of the systematic errors investigated by Rossetti & Molendi and Nevalainen et al. taking into account the whole sample of the PDS observations off the Galactic plane, as already shown in our data analysis of Abell 2256 (Fusco-Femiano, Landi & Orlandini). All this eliminates any ambiguity and confirms the presence of a hard tail in the spectrum of the Coma cluster.
  • cosmic microwave background
  • galaxies: clusters: individual (Coma)
  • magnetic fields
  • radiation mechanisms: nonthermal
  • X-rays: galaxies