We present a detailed analysis of the cluster of galaxies Abell 496 .
The optical data include a redshift catalogue of 466 galaxies , out of which 274 belong to the main cluster and a CCD photometric catalogue in a much smaller region , with 239 and 610 galaxies in the V and R bands respectively .
The X-ray analysis is based on an image obtained with the ROSAT PSPC . Besides Abell 496 itself , the velocity distribution along the line of sight shows the existence of at least four structures at different redshifts , one of them seeming to be a poor cluster at a velocity of 30083 km/s .
The other of these structures have a too large spatial extent to be clusters but may be filaments along the line of sight or other young structures . Various independent methods show that Abell 496 appears to be a quite relaxed cluster , except perhaps for the distribution of emission line galaxies .
These appear to be distributed in two samples falling on to the main cluster , one from the back ( the ELGs concentrated towards the west ) and one from the front ( the high velocity ELGs ) . The bright part of the galaxy luminosity function , built from the redshift catalogue , shows a flattening at R \sim 16 ( M _ { R } \sim - 20.5 ) , and can be accounted for by a gaussian distribution of bright galaxies and a power law or Schechter function for faint galaxies .
The deeper galaxy counts derived from CCD imaging show a dip at R \sim 19.5 ( M _ { R } \sim - 17 ) which can be modelled assuming a cut-off in the luminosity function such as that observed in Coma . We propose a model for the X-ray gas and derive the galaxy , X-ray gas and total dynamical masses , as well as the baryon fraction in the cluster .
Abell 496 appears as a relaxed cluster which can be used as a prototype for further studies .