THE RICH CLUSTER OF GALAXIES ABCG 85 - III - ANALYZING THE ABCG-85 87/89 COMPLEX/

We present a combined X-ray and optical analysis of the ABCG 85/87/89 complex of clusters of galaxies, based on the ROSAT PSPC image, optica l photometric catalogues (Slezak et al. 1998), and an optical redshift catalogue (Durret et al. 1998). From this combined data set, we find striking alignments at all scales at PA similar or equal to 160 degree s. At small scales, the cD galaxy in ABCG 85 and the brightest galaxie s in the cluster are aligned along this PA. At a larger scale, X-ray e mission defines a comparable PA south-southeast of ABCG 85 towards ABC G 87, with a patchy X-ray structure very different from the regular sh ape of the optical galaxy distribution in ABCG 87. The galaxy velociti es in the ABCG 87 region show the existence of subgroups, which all ha ve an X-ray counterpart, and seem to be falling onto ABCG 85 along a f ilament almost perpendicular to the plane of the sky. To the west of A BCG 85, ABCG 89 appears as a significant galaxy density enhancement, b ut is barely detected at X-ray wavelengths. The galaxy velocities reve al that in fact this is not a cluster but two groups with very differe nt velocities superimposed along the line of sight. These two groups a ppear to be located in intersecting sheets on opposite sides of a larg e bubble. These data and their interpretation reinforce the cosmologic al scenario in which matter, including galaxies, groups and gas, falls onto the cluster along a filament.