VLA OBSERVATIONS OF THE RICH X-RAY-CLUSTER ABELL-2256

The complex radio emission from the rich X-ray cluster of galaxies Abell 2256 has been mapped at 20 cm using the VLA in A, B, C, and D configurations and at 90 cm using the VLA in B configuration. The observations give detailed information about radio structures on scales up to 10 arcminutes with an angular resolution of 1''.5 and with an unprecedented signal-to-noise ratio. The properties of the northern radio halo, the numerous head-tail sources and a unique ultra-steep spectrum source are discussed, taking into account the recent results of the ROSAT X-ray satellite. The northern halo of Abell 2256 has a remarkable morphology, It has sharp edges and possible filamentary structure. The origin of this halo is discussed. We suggest that the region contains two or three head-tail galaxies that are heavily distorted due to the infalling subcluster that has been inferred from the ROSAT data. We find that one radio tail extends to at least about 700 kpc from its parent galaxy and seems morphologically disconnected from the cluster halo. From the small deviations from the remarkable straightness of this source, we estimate the turbulence in the confining X-ray gas around this source to be similar to 200 km s(-1) on scales of about 20 kpc. The nature of the ultrasteep spectrum source is unclear. The source, with a spectral index of -1.6, has a Z-shaped morphology and is extended by similar to 4'. We tentatively identify it with a cluster galaxy coincident with the eastern ''flatter'' region. The ultrasteep spectrum source may be a head-tail radio galaxy with peculiar morphology. The overall conclusion from the radio data is that the remarkable radio properties of Abell 2256 can be explained within the merging subcluster model as due to both the high velocity dispersion of the cluster galaxies and the high gas density of the intercluster medium which both contribute to shaping the radio morphologies.