XXL调查：XLIII。通过结合COSMOS和XXL-S X射线选择类星体的结果得到的射电光度函数揭示了类星体射电响度二分法
The XXL Survey: XLIII. The quasar radio loudness dichotomy exposed via radio luminosity functions obtained by combining results from COSMOS and XXL-S X-ray selected quasars
摘要：
我们研究了274个无线电和X射线选择类星体（XQSO）在COSMOS和XXL-S无线电调查中检测到的样本在3 GHz和2.1 GHz，分别。这个样本是通过采用一个保守的X射线光度阈值Lx [2-10\ keV] >= 10^44 erg/s来识别的，只选择了最强大的类星体。使用现有的多波长数据，我们研究了各种标准的无线电响亮（RL）和无线电安静（RQ）XQSO的选择，发现RL/RQ XQSO的数量变化显着取决于所选择的标准。这种差异的产生是由于追踪不同物理过程的不同标准，以及由于我们的样本是从通量限制的无线电和X射线调查中选择的。另一种研究类星体射电辐射起源的方法是通过它们的射电光度函数（RLF）。我们在0.5 <= z <= 3.7的六个红移仓中构造了XQSO 1.4 GHz射电光度函数（RLF）。较低的1.4 GHz的光度端显示出更高的归一化比预期的只有从活动星系核的贡献，在所有研究的红移箱。所发现的“凸点”主要是由于XQSO宿主星系内的恒星形成（SF）过程的排放。正如预期的那样，活动星系核相关的射电辐射在RLF的高光度端占主导地位。通过结合文献中的解析形式，研究了XQSO RLF的演化，以限制RLF中的低光度“凸点”和高光度活动星系核部分。我们定义了两个1.4GHz的亮度阈值，Lth，SF和Lth，AGN，在这两个阈值之下和之上，80%以上的对RLF有贡献的源分别由SF和AGN相关的活动所支配。这些阈值随红移而变化，很可能是由于XQSO宿主星系的SFR的强烈演化。
英文摘要：
We studied a sample of 274 radio and X-ray selected quasars (XQSOs) detected in the COSMOS and XXL-S radio surveys at 3 GHz and 2.1 GHz, respectively. This sample was identified by adopting a conservative threshold in X-ray luminosity, Lx [2-10\ keV] >= 10^44 erg/s, selecting only the most powerful quasars. Using available multiwavelength data, we examined various criteria for the selection of radio-loud (RL) and radio-quiet (RQ) XQSOs, finding that the number of RL/RQ XQSOs changes significantly depending on the chosen criterion. This discrepancy arises due to the different criteria tracing different physical processes and due to our sample being selected from flux-limited radio and X-ray surveys. Another approach to study the origin of radio emission in XQSOs is via their radio luminosity function (RLF). We constructed the XQSO 1.4 GHz radio luminosity functions (RLFs) in six redshift bins at 0.5 <= z <= 3.7. The lower-1.4 GHz luminosity end shows a higher normalization than expected only from AGN contribution in all studied redshift bins. The found "bump" is mostly dominated by emission due to star-forming (SF) processes within the XQSO host galaxies. As expected, AGN-related radio emission dominates at the higher-luminosity end of RLF. The evolution of XQSO RLF was studied via combination of analytic forms from the literature to constrain the lower-luminosity "bump" and the higher-luminosity AGN part of the RLF. We defined two 1.4 GHz luminosity thresholds, L_th,SF and L_th,AGN, below and above which more than 80% of sources contributing to the RLF are dominated by SF and AGN-related activity, respectively. These thresholds evolve with redshift, most likely due to the strong evolution of SFRs of the XQSO host galaxies.
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