The extragalactic radio sources are divided into two subclasses (radio-loud and radio-quiet sources) in the literature using radio loudness (R), which is defined as the ratio of radio emission to optical emission, but the boundary R-value separating the two classes is different in various sources. In this work, a sample of 2419 objects from the 13th catalog of quasars and active nuclei is used to build a boundary for the two subclasses. To do so, we compiled the radio and optical data, calculated their radio and optical indexes, made K-correction, obtained the radio loudness, and adopted a Bayesian analysis method to the logarithm of radio loudness for classification. We also investigated the correlations of radio loudness with radio/optical luminosities. Our main conclusions are summarized as follows: (1) The distribution of the logarithm of radio loudness (log R) is bimodal, the sources with log R < 1.26 are classified as radio-quiet sources, and those with log R > 1.26 are classified as radio-loud ones from the Bayesian analysis method. (2) The average radio-optical effective spectral index of radio-quiet sources is 〈αRO〉 = 0.05, while that of radio-loud sources is 〈αRO〉 = 0.55. (3) There are positive correlations between radio luminosity and radio loudness for both radio-loud sources and radio-quiet sources. (4) A dividing line of separating the distribution of the clusters on the diagram of radio loudness against radio luminosity was obtained statistically to set the boundary between radio-loud sources and radio-quiet sources, with an accuracy of $99.73\%$ based on the classification result from the Bayesian analysis method.

中文翻译：

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无线电源的无线电响度和分类

文献中使用无线电响度 (R) 将河外无线电源分为两个子类（无线电响度和无线电静源），无线电响度 (R) 定义为无线电发射与光学发射的比率，但边界 R 值将两个类在各种来源中是不同的。在这项工作中，来自第 13 个类星体和活动核目录的 2419 个物体的样本用于为这两个子类建立边界。为此，我们整理了无线电和光学数据，计算了它们的无线电和光学指标，进行了K校正，得到无线电响度，并采用贝叶斯分析方法对无线电响度的对数进行分类。我们还研究了无线电响度与无线电/光学光度的相关性。我们的主要结论总结如下：(1) 无线电响度对数(log R)的分布是双峰的，log R < 的源 1.26 被归类为无线电静噪源，log R > 根据贝叶斯分析方法，1.26 被归类为无线电响亮的。(2)射电静源的平均射电有效光谱指数为<αRO>=0.05，而射电响源的平均射电有效光谱指数为<αRO>=0.55。(3) 无线电响源和无线电静源的无线电光度和无线电响度之间存在正相关关系。(4) 统计求出射电响度与射电光度图上簇分布的分界线，确定射电响源与射电静源的分界线，准确度为$99.73\%$，基于贝叶斯分析方法的分类结果。