X-ray spectrum of the 2A 0335+096 cluster of galaxies

Abstract

We present the X-ray spectrum of a poor cluster of galaxies 2A 0335 + 096 obtained with the medium energy and the gas scintillation proportional counter experiments on board EXOSAT. The observed spectrum is best explained by a thermal bremsstrahlung emission process from a hot intracluster gas with a temperature of ~3.4×10⁷ K, and a line at 6.5 keV arising from transitions in highly ionized iron, i.e., Fe XXIV, Fe XXV, and Fe XXVI, which is redshifted to the observed peak energy. An iron abundance value of 0.4 times the solar value is derived for the hot gas in the cluster. The 99 percent confidence range derived for the iron abundance is 0.2-0.55 times the solar value, making it one of the most precise measurements of an iron line in X-ray clusters of galaxies. The iron abundance is remarkably similar to the values found for rich clusters and, therefore, is indicative of a universal value of iron abundance in all the X-ray clusters irrespective of their evolutionary and dynamical states.