THE RICH CLUSTER OF GALAXIES ABCG-85 .1. X-RAY-ANALYSIS

We present an X-ray analysis of the rich cluster ABCG 85 based on ROSA T PSPC data. By applying an improved wavelet analysis, we show that ou r view of this cluster is notably changed from what was previously bel ieved (a main region and a south blob). The main emission comes from t he central part of the main body of the cluster on which is superimpos ed that of a foreground group of galaxies. The foreground group and th e main cluster are separated (if redshifts are cosmological) by 46 h(5 0)(-1) Mpc. The southern blob is clearly not a group: it is resolved i nto X-ray emitting galaxies (in particular the second more luminous ga laxy of the main cluster). Several X-ray features are identified with bright galaxies. We performed a spectral analysis and derived the temp erature (T), metallicity (Z) and hydrogen column density (N-H) The glo bal quantities are: T=4 keV (in agreement with the velocity dispersion of 760 km/s) and Z=0.2Z.. We cannot derive accurate gradients for the se quantities with our data, but there is strong evidence that the tem perature is lower (similar to 2.8 keV) and the metallicity much higher (Z similar to 0.8Z.) in the very centre (within about 50 h(50)(-1) kp c). We present a pixel by pixel method to model the physical propertie s of the X-ray gas and derive its density distribution. We apply class ical methods to estimate the dy namical, gas and stellar masses, as we ll as the cooling time and cooling flow characteristics. At the limiti ng radius of the image (1.4 h(50)(-1) Mpc), we find M-dyn similar to ( 2.1 - 2.9)10(14) h(50)(-1) M., M-gas/M-dyn similar to 0.18 h(50)(-1.5) . The stellar mass is 6.7 10(12) M., giving a mass to light ratio of M /L-V N 300 h(50). The cooling time is estimated for different models, leading to a cooling radius of 30-80 kpc depending on the adopted clus ter age; the mass deposit rate is 20-70 M./yr, lower than previous det erminations. These results are discussed (cooling flow paradigm in rel ation with high Z, 'baryonic crisis' etc.) in connection with current ideas on dynamical and evolutionary properties of clusters.