Abstract:
The V/Vmax analysis is a powerful method to study quasar density distribution and luminosity evlution, but the observed sample N(>lmin, n) can not be regarded as complete when used to investigate the density law in the range of zN and intrinsic luminosities of different sources in the sample are different, so that, to a certain extent, the results of usual procedure are not reliable enough. We present an idea that the quasar L-z curve, from which the deviation of actual sources obeys a certain probability distribution, can be obtained by statistics, and then, the incompleteness factor K(z|lmin)for each source can be given. In this paper we adopt the regression iteration procedure with censored data, assuming deviation of quasar sources from L-z curve follows normal distribution approximately, and analyze the SCRand 4Csamples. On 90% confidence level the space density distribution of quasars is relative to q0 For q0=0, quarsar are close to homogeneous distribution. For q0=1/2, the quasar number increases slightly with the increase of redshift. Only for q0=1, quasars have a strong cosmological evolution. The value of 2 to 6 of the parameter r of density law in the case q0=1 is smaller than that of 10 to 12 derived by previous V/Vmax test, so it is relatively more consistent with the theoretical model to explain quasar form and density evolution in virtue of low density of intergalactic medium. The 3CR sources detected in X-ray are also analyzed, which shows our revised method with incompleteness factors can characterize the sample in different wave band regions.
