1999/02/01 by M. Henriksen, M. J. Henriksen · 2 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #Solar and Space Plasma Dynamics #astro-ph
paper · pdf · doi:10.1086/306729
published as Astrophys.J. 511 (1999) 666 · 8 pages, Astrophysical Journal (in press)
openalex publication_date 1999/02/01 · arxiv created 1999/03/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
An 8.3 hr observation of the Abell 2256 galaxy cluster using the Rossi X-Ray Timing Explorer proportional counter array produced a high-quality spectrum in the 2-30 keV range. Joint fitting with the 0.7-11 keV spectrum obtained with the ASCA gas imaging spectrometer gives an upper limit of ~2.3 × 10 −7 photons cm -2 s -1 keV -1 for nonthermal emission at 30 keV. This yields a lower limit to the mean magnetic field of 0.36 μG and an upper limit of 1.8 × 10 −13 ergs cm -3 for the cosmic-ray electron energy density. The resulting lower limit to the central magnetic field is ~1-3 μG. While a magnetic field of ~0.1-0.2 μG can be created by galaxy wakes, a magnetic field of several microgauss is usually associated with a cooling flow or, as in the case of the Coma Cluster, a subcluster merger. However, for A2256 the evidence for a merger is weak and the main cluster shows no evidence of a cooling flow. Thus there is presently no satisfactory hypothesis for the origin of an average cluster magnetic field as high as greater than 0.36 μG in the A2256 cluster.