THE CLUSTER DYNAMICS, X-RAY-EMISSION, AND RADIO GALAXIES IN ABELL-578AND ABELL-1569

We present the results of our multiwavelength study of two nearby Abel l clusters that contain extended tailed radio sources. From our analys is of archival PSPC x-ray data, VLA radio observations, and new veloci ty measurements, we find strong evidence that these clusters are not r elaxed. Significant x-ray substructure is revealed by examining deviat ions from circular models of the overall x-ray surface brightness maps . We report 130 new redshifts from the fields of A578 and A1569 and fi nd that 41 galaxies belong to A578 and 54 belong to A1569. Moreover, w e detect the presence of substructure in the velocity and spatial dist ribution of galaxies. We identify two interacting subclusters in A578 and two gravitationally unbound subclusters in A1569. Furthermore, we find that the radio sources in A578 are at rest with respect to their subclusters and that the wide-angled tailed (WAT) source in A1569 has a small peculiar motion with respect to its subcluster (220 km/s). The standard model of ram pressure induced jet curvature requires relativ e velocities of the radio sources with respect to the ICM of greater t han or similar to 1000 km/s. Therefore, the apparent peculiar velociti es of the radio galaxies cannot explain the bending of the jets/tails for the narrow-angled tailed (NAT) radio source in A578 and for the WA T in A1569. We suggest that a cluster-subcluster merger model provides a reasonable explanation for the x-ray and optical substructure detec ted in these systems. Numerical simulations of cluster-subcluster merg ers predict a bulk flow of ICM gas that has sufficient dynamic pressur e for bending and shaping the extended radio sources. Thus, a cluster- subcluster merger can provide the environment responsible for the obse rved cluster x-ray and optical morphologies and for the bending seen i n the radio sources. (C) 1997 American Astronomical Society.