paper

The peculiar cooling flow cluster RX J0820.9+0752

arXiv:astro-ph/0208254 · doi:10.1046/j.1365-8711.2002.05969.x

Abstract

(Abridged) We present observations of the cluster of galaxies associated with the X-ray source RX J0820.9+0752 and its dramatic central cluster galaxy (CCG) in the optical and X-ray wavebands.Unlike other cooling flow CCGs studied in detail, this system does not contain a powerful radio source at its core, and so provides us with an important example where we expect to see only the processes directly due to the cooling flow itself. Chandra observations show that the hot intracluster gas is cooling, dropping below 1.8 keV in the core. Optical images (AAT and HST) show that the central galaxy is embedded in a luminous line-emitting nebula that coincides spatially with an excess of X-ray emission, and separate, off-nucleus clumps of blue continuum that form part of a patchy structure arcing away from the main galaxy. The X-ray/H-Alpha feature is reminiscent of a filament observed in A 1795 which is suggested to be a cooling wake, produced by the motion of the CCG through the ICM. We present optical spectra of the CCG and its surroundings, and find that the continuum blobs show poperties clearly distinct from those of the surrounding nebula. Accounting for the strong intrinsic reddening and its significant variation over the extent of the line emitting region, we have fit the continuum spectra of the blobs and the nucleus using stellar spectra. We found that continuum emission from early main sequence stars can account for the blue excess light in the blobs. Kinematical properties associate the gas in the system with a nearby galaxy, suggesting some kind of tidal interaction between the two. We suggest that the secondary galaxy has moved through the cooling wake produced by the CCG, dragging some of the gas out of the wake and triggering the starbursts found in the blobs.

16 pages, 12 figures, submitted to MNRAS

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