We present observations of the cluster of galaxies associated with the X-ray source RX J0820.9+0752 and its dramatic central cluster galaxy in the optical and X-ray wavebands .
Unlike other cooling flow central cluster galaxies 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 .
A 9.4 ks Chandra observation shows that the hot intracluster gas is cooling within a radius of 20 kpc at a rate of a few tens of solar masses per year .
The temperature profile is typical of a cooling flow cluster and drops to below 1.8 keV in the core .
Optical images taken with the AAT and HST show that the central galaxy is embedded in a luminous ( L _ { H \alpha } \sim 5 \times 10 ^ { 42 } { \thinspace erg } { \thinspace s } ^ { -1 } ) , extended line-emitting nebula that coincides spatially with a bright 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 the 40 kpc long filament observed in A 1795 which is suggested to be a cooling wake , produced by the motion of the central cluster galaxy through the intracluster medium .
We present optical spectra of the central cluster galaxy and its surroundings , and find that the continuum blobs show stronger line emission , differing kinematic properties and more extreme ionization ratios than 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 empirical stellar spectra from a library .
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 secondary 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 central cluster galaxy , dragging some of the gas out of the wake and triggering the starbursts found in the blobs .