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Session 95 - X-Ray Galaxies and Clusters.
Oral session, Wednesday, January 17
La Condesa, Hilton
New X-ray observations are presented for 9 Abell clusters which contain wide-angle tailed (WAT) radio galaxies. These clusters were observed with the PSPC on board the ROSAT observatory. The sample of WAT clusters was selected from a VLA radio survey of the Abell catalog at 20-cm and the ROSAT-all-sky-survey (RASS). We found an important correlation between the X-ray morphology and the radio sources: there is a strong correlation between the orientation of the WAT tails and the direction of X-ray elongations within the core of the clusters. Moreover, we found that 90% of the clusters show an irregular and clumpy X-ray emission with at least 70% of the clusters showing significant X-ray substructure. These clusters also show evidence of isophotal twisting, ellipticity variation, and isophote centroid variation as a function of distance from the central X-ray peak. Additionally, none of these WAT clusters have evidence of significant cluster-wide cooling flows in spite of the presence of optically-bright D (radio) galaxies. We believe that these results are consistent with WAT clusters undergoing mergers with groups or subclusters of galaxies. We compared our results with numerical Hydro/N-Body simulations of merging galaxy clusters to test this hypothesis. We found that the X-ray synthetic images generated by the simulations reproduce all the major morphological properties that we found in our sample. Furthermore, the simulations also show that the bulk flow of gas within the ICM present during the merger could be responsible for the correlation between the X-ray elongations and the direction of the bending of the radio tails.
This work was partially supported by NASA through grants NAGW-3152 and NAG5-1819, and by the NSF through grant AST93-17596.
Program listing for Wednesday