The spatial correlation function from an X-ray selected sample of Abell clusters

We present here the Spatial Two--Point Correlation Function for a completesample of 67 X--ray selected Abell clusters of galaxies. We find a correlationlength of $16.1\pm3.4\mpc$ with no significant clustering beyond$\simeq40\mpc$. This is the lowest uncorrected value for the correlation lengthever derived from the Abell catalogue of clusters. In addition, we haveinvestigated the anisotropy of the correlation function between the radial andtransverse directions. This can be characterised by the magnitude of pair--wisecluster peculiar velocities such anisotropy predicts, which we find to be$\simeq800{\rm km\,s^{-1}}$ for our sample. Again, this is the lowestuncorrected value ever seen for the Abell catalogue. We therefore, no longerneed to invoke high cluster peculiar velocities or line of sight clustering tounderstand the correlation function as derived from an Abell sample ofclusters. Furthermore, our result is consistent with recently publishedcorrelation functions computed from automated selections of optical and X--rayclusters. Therefore, we are now approaching a coherent picture for the form ofthe cluster spatial correlation function which will be used to place confidentconstraints on theories of galaxy formation.Comment: 11 pages, Latex fil