BeppoSAX observation of the rich cluster of galaxies Abell 85

Abstract

We report the observation of the Intra-Cluster Medium (ICM) of Abell 85 by the X-ray satellite BeppoSAX. We have analysed both the spectrum obtained in the central 8 arcmin circular region centred on the Very Steep Spectrum Radio Source (VSSRS) and the spectra from a number of sub-regions. Analysis of the spectra allowed us to independently obtain new estimates of the temperature, metallicity and line-of-sight hydrogen density column, both globally (T = 6.6 ± 0.3 keV, Z = 0.38 ± 0.06 Z⊙ and NH = 5.5-0.7+0.9 1020 cm-2) and locally. These measures are in good agreement with previous measures based on ROSAT and ASCA data. In the region of the VSRSS, we attempted to discriminate between thermal and non-thermal X-ray emission. Although we could not do this unambiguously, we have nonetheless estimated the extended magnetic field using the radio spectrum available for this region. We obtain a lower limit intensity of 0.9 μG, consistent with our previous estimate. We also derive α-elements/iron abundance ratios that turn out to be higher than 1. Such a result tends to support the burst model for elliptical galaxies, where a strong galactic wind develops early in the galaxy history and type II supernovae (SN) may be the major contributors to the enrichment of the ICM. A two-temperature ICM model was fitted in the central region, yielding a main component with roughly the mean cluster temperature and a cooler component with temperature less than 0.1 keV.