The luminosity function is an essential tool for determining the evolution of AGN and their contribution to cosmic backgrounds. Binned differential luminosity functions constructed using the 1/Va method have a systematic error for objects close to their parent sample's flux limit(s). This is particularly noticable when luminosity functions are produced for a number of different redshift ranges as is common in the study of AGN or galaxy evolution. A simple method of constructing a binned luminosity function which overcomes this problem is presented. Binned luminosity functions produced by the two methods are compared for simulated data and for the Large Bright QSO Survey (LBQS). It is shown that the 1/Va method produces a misleadingly complex picture of evolution in the LBQS.

Back to the programme
Main workshop page