Evolution in the X‐Ray Cluster Luminosity Function Revisited

(Shortened Abstract) We present new X-ray data taken from the ROSAT PSPCpointing archive for 21 clusters in the Einstein Extended Medium SensitivitySurvey (EMSS). We have supplemented these data with new optical follow-upobservations found in the literature and overall, 32 of the original 67 z>0.14EMSS clusters now have new information. Using this improved EMSS sample, wehave re-determined the EMSS X-ray Cluster Luminosity Function as a function ofredshift. We have removed potential mis-classifications and included our newmeasurements of the clusters X-ray luminosities and redshifts. We find similarluminosity functions to those originally presented by Henry etal (1992); albeitwith two important differences. First, we show that the original low redshiftEMSS luminosity function is insufficiently constrained. Secondly, the power lawshape of our new determination of the high redshift EMSS luminosity function(z=0.3 to 0.6) has a shallower slope than that seen by Henry etal. We havequantified the degree of evolution seen in the X-ray cluster luminosity usingseveral statistical tests. The most restrictive analysis indicates that our lowand high redshift EMSS luminosity functions are statistically different at onlythe 95% level. However, other tests indicate that these luminosity functionsdiffer by as little as one sigma. These data are therefore, consistent with noevolution in the X-ray cluster luminosity function out to z=0.5.