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M. Gitti (Ohio University), L. Feretti (IRA - INAF Bologna), S. Schindler (Inst. of Astrophysics, Innsbruck University)
We report on the peculiar activity of the radio source located at the center of the cooling flow cluster RBS797 (z=0.35), the first distant cluster in which two pronounced X-ray cavities have been discovered. The new multifrequency (1.4, 4.8 and 8.4 GHz) observations obtained with the Very Large Array (VLA) reveal clearly the presence of radio emission on three different scales showing orientation in different directions. Particularly remarkable is that the inner radio jets on kpc scale are oriented in a direction perpendicular to that of the extended structure detected at lower resolution, which is elongated exactly towards the holes detected in X-rays. We therefore find evidence of a strong interaction between the central radio source and the intra-cluster medium in RBS797. We suggest a scenario in which the 1.4 GHz emission filling the X-ray cavities consists of buoyant bubbles of radio emitting plasma created by twin jets in the past whose expansion has displaced the thermal gas that was formerly in the X-ray holes, whereas the two jets visible at 4.8 GHz are related to the present nuclear activity which has restarted at a position angle different from the original outburst that created the outer radio lobes. This work was supported by the Austrian Science Foundation FWF under grant P15868 and by the Tiroler Wissenschaftsfonds.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.