OSO 8 x-ray spectra of clusters of galaxies. I. Observations of twenty clusters: Physical correlations

OSO 8 X-ray spectra from 2 to 20 keV have been analyzed for 26 clusters of galaxies. For 20 clusters we present temperatures, emission integrals, iron abundances,and low energy absorption measurements. Our data give, in general, better fits to thermal bremsstrahlung than to power-law models. Eight clusters have positive iron emission-line detections at the 90% confidence level, and all 20 cluster spectra are consistent with Fe/H=1.4 x 10-5 by number with the possible exception of Virgo. Thus we confirm that X-ray emission in our energy band is predominantly thermal radiation from hot intracluster gas rather than inverse Compton radiation.Physical correlations between X-ray spectral parameters and other cluster properties are examined. We find that (1) the X-ray temperature is approximately proportional to the square of the velocity dispersion of the galaxies; (2) the emission integral, and therefore the bolometric X-ray luminosity, is a strong function of the X-ray temperature; (3) the X-ray temperature and emission integral are better correlated with cluster central galaxy density than with richness; (4) the temperature and emission integral are separately correlated with Rood-Sastry type; and (5) the fraction of galaxies which are spirals is correlated with the observed ram pressure in the cluster core. The physical implications of these data are discussed