类星体样本的不完备性补偿因子和V/V<SUB>max</SUB>分析

刘祖伟; 张和祺

doi:10.11728/cjss1985.01.001

类星体样本的不完备性补偿因子和V/V_max分析

doi: 10.11728/cjss1985.01.001

中国科学院紫金山天文台

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出版历程
- 收稿日期: 1984-02-22
- 修回日期: 1900-01-01
- 刊出日期: 1985-01-24

Factors for Incompleteness of QSO's Sample and V/V_max Analysis

Purple Mountain Observatory, Academia Sinica

摘要

摘要: 本文采用截尾回归迭代程序给出源的光度-红移关系曲线.在假定实际源偏离此曲线而服从正态分布情况下, 给出每一源的不完备性补偿因子.用经修改的V/V_max方法, 分析了3CR和4C的光学、射电样本以及3CR的X射线光度样本.在置信度90％的水平, 类星体的空间分布与q₀有关.只有q₀=1时, 类星体才随红移有明显的宇宙学演化, 且这时密度分布规律中的参数γ值为2—6, 小于以往V/V_max分析所得10—12的γ值.这与用星系际低密度介质说明类星体生成和密度演化的理论解释一致.分析还表明补偿因子法能反映样本在不同波段的特性.

Abstract: The V/V_max analysis is a powerful method to study quasar density distribution and luminosity evlution, but the observed sample N(>l_min, 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|l_min)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.