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The US Survey and the Incidence of Bright Quasars

机译:美国调查和明亮类星体的发病率

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摘要

The bright quasar sample from the US survey (UBQS) comprises 19 quasars with B 16.95 mag selected within the areal completeness boundaries of seven US survey fields. A subset of 17 quasars is statistically complete for objects judged to be starlike on images taken with cameras of the 1.2 m Schmidt class that satisfy the morphological criterion B 21-[3/(4z)], where B 18.5 mag, at redshift z. Twelve objects compose a statistically complete subset that satisfies criteria on absolute magnitude MB -23.0 (where H0 = 50) and z 0.3. These subsets and others defined by other morphological criteria currently in use confirm the high incidence of bright US survey quasars previously established with the MB criterion alone. The number count data and the redshift distribution for the bright quasars of the UBQS are found to agree with those of the Hamburg ESO (HES) and Edinburgh quasar surveys (EQS). The number counts in the range 15.5 B 16.95 from these three quasar samples are consistently higher than those produced from other published quasar samples in the same magnitude range. These results suggest that the UBQS, HES, and EQS approach statistical completeness within the limits of their respective selection criteria. Surface densities from these three quasar samples favor the semiempirical fit of luminosity-dependent luminosity evolution (LDLE) of LaFranca and Cristiani. An observed excess of quasars in the range 0.5 z ≤ 0.6 is discussed. The apparent overabundance does not appear to be a result of selection effects. The present data will be useful in recalculating the LDLE fit parameters.
机译:来自美国调查(UBQS)的明亮类星体样本包括19个类星体,这些类星体在七个美国调查场的区域完整性边界内选择了B <16.95 mag。对于用1.2 m Schmidt类相机满足形态学标准B <21- [3 /(4z)],其中B <18.5 mag,红移的情况下被判断为星状的图像,统计上17个类星体的子集是完整的z。 12个对象组成了一个统计上完整的子集,该子集满足绝对值MB <-23.0(其中H0 = 50)且z> 0.3的条件。这些子集以及其他当前由其他形态学标准定义的子集证实了以前仅通过MB标准建立的明亮的美国调查类星体的发生率很高。 UBQS明亮类星体的数量计数数据和红移分布与汉堡ESO(HES)和爱丁堡类星体调查(EQS)的数据一致。从这三个类星体样本获得的15.5

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