Abstract
Clusters of galaxies were established as a class of X-ray sources by observers on the Uhuru satellite (Gursky et al. 1971). These early results indicated that clusters were a powerful (Lx in the 2–6 keV band > 1044 erg/sec) and numerous (≳ 9) class of extra-galactic X-ray sources. These early results also indicated that the sources were extended (Kellogg 1972; Kellogg and Murray 1974) with a characteristic size ≳ .25 Mpc. Early spectral data (Kellogg, Baldwin and Koch 1974; Catura et al. 1972; Gorenstein et al. 1973) showed that the spectra were not strongly cutoff at low energies and could be fit equally well by power laws of energy index ∿ 1 or by the emission from optically thin hot gas (henceforth referred to as thermal bremsstrahlung and abbreviated as T—B) with a temperature of ∿ 108 °K.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
