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Q. D. Wang (UMass), F. Owen (NRAO), M. Ledlow (Gemini Obs.)
The structure of the universe is believed to have formed by clustering hierarchically from small to large scales. Much of this evolution occurs very slowly but at a few special times more, rapid, violent activity may occur as major subunits collide at high velocities. Abell 2125 (z=0.247) appears to be undergoing such an event as shown by modeling of the optical velocity field and by the detection with the VLA of an unusually large number of associated radio active galaxies. The core of the cluster contains four strong radio galaxies, one of which (C153) as imaged by HST shows a very peculiar, disrupted morphology and a radial velocity of 2000 km/s relative to the cluster mean. We present a spectacular 80 ksec Chandra imaging of Abell 2125. This X-ray imaging, together with extensive complementary multi-wavelength data (see the accompanied presentation by Keel et al.), reveals for the first time the direct evidence for galaxy transformation and destruction during the cluster formation. The Chandra data unambiguously separate the X-ray contributions from discrete sources and large-scale diffuse gas in the Abell 2125 complex, which consists of various merging clusters/groups of galaxies and low-surface brightness emission. This enables us to study processes affecting galaxy evolution during this special time from scales of Mpc down to a few Kpc. On large scales, a patch of relatively prominent low-surface brightness X-ray emission has a significantly lower temperature metal abundance than in the Abell 2125 core cluster, characteristic of a group environment. At higher resolution, soft X-ray enhancements are found to be associated with bright radio galaxies in the core cluster. A distinct X-ray trail, in particular, appears on one side of C153 suggesting that the ISM is being stripped from this galaxy. The overall level of activity plus the special time for the cluster-cluster merger suggests that an important phase of galaxy evolution can take place during such events.
This work was supported by NASA through Chandra grant GO1-2126.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.