Title: Disclosing the Radio Loudness Distribution Dichotomy in Quasars: An Unbiased Monte Carlo Approach Applied to the SDSS-FIRST Quasar Sample Show Chinese title

Title: 揭示类星体射电明亮度分布的二分法：应用于SDSS-FIRST类星体样本的无偏蒙特卡罗方法

Abstract: We investigate the dichotomy in the radio loudness distribution of quasars by modelling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8,300 quasars drawn from the SDSS DR7 Quasar Catalog and combined with radio observations from the FIRST survey. Our results indicate that the SDSS-FIRST sample is best described by a radio loudness distribution which consists of two components, with 12+/-1 % of sources in the radio-loud component. On the other hand, the evidence for a local minimum in the loudness distribution (bimodality) is not strong and we find that previous claims for its existence were probably affected by the incompleteness of the FIRST survey close to its faint limit. We also investigate the redshift and luminosity dependence of the radio loudness distribution and find tentative evidence that at high redshift radio-loud quasars were rarer, on average "louder", and exhibited a smaller range in radio loudness. In agreement with other recent work, we conclude that the SDSS-FIRST sample strongly suggests that the radio loudness distribution of quasars is not a universal function, and that more complex models than presented here are needed to fully explain available observations. Show Chinese abstract

Abstract: 我们通过使用蒙特卡洛方法对类星体的射电辐射和各种选择效应进行建模，研究类星体射电明亮度分布中的二分法。 射电明亮和射电安静类星体两种物理上不同的类星体群体的存在是有争议的，并且在过去十年中，类星体射电明亮度的双峰分布既被确认也被质疑。 我们用简单的单峰和双峰分布函数对类星体射电光度分布进行建模。 结果模拟样本与从SDSS DR7类星体目录中选出的8300个基准样本以及来自FIRST调查的射电观测数据相结合进行比较。 我们的结果表明，SDSS-FIRST样本最好由一个由两个成分组成的射电明亮度分布来描述，其中12±1%的源位于射电明亮成分中。 另一方面，明亮度分布中的局部最小值（双峰性）的证据并不强烈，我们发现以前关于其存在的声明可能受到了FIRST调查接近其暗极限时不完整的影晌。 我们还研究了射电明亮度分布的红移和光度依赖性，并发现初步证据表明，在高红移时，射电明亮类星体较少，平均“更响”，并且在射电明亮度范围上较小。 与其他最近的研究一致，我们得出结论，SDSS-FIRST样本强烈表明类星体的射电明亮度分布不是一个通用函数，并且需要比这里提出的更复杂的模型来完全解释现有的观测结果。