核心优势参数与河外射电源的\emph{Fermi}探测
The core dominance parameter and \emph{Fermi} detection of extragalactic radio sources
摘要：
本文利用\emph{Fermi} -LAT第三源表（3FGL）对542个河外射电源的存档样本进行了交叉相关，编制了一个包含80个$γ$射线源和462个非\emph{Fermi}源的样本，这些源具有可用的核心优势参数（$R_{CD}$）、核心和扩展射电光度;所有参数都是直接测量的或从文献中的可用数据导出的。发现$R_{CD}$分别与射电核心光度、$γ$射线光度和$γ$射线通量有显著的相关性，\emph{Fermi}源的$R_{CD}$平均值高于非\emph{Fermi}源.这些结果表明，\emph{Fermi}源应更紧凑，聚束效应对探测$γ$射线发射起着至关重要的作用。此外，我们的结果还表明，在固定的$R_{CD}$下，\emph{Fermi}源比非\emph{Fermi}源具有系统性的更大的射电通量，这表明\emph{Fermi}源具有更大的内禀射电通量。这些结果表明，对于本样品，无线电和$γ$ -射线通量之间有很强的联系，并表明非\emph{Fermi}源可能是由于低聚束效应和/或低固有$γ$ -射线通量，支持文献中的情景：无线电和$γ$射线发射的活动的共空间起源，这表明用于高能$γ$射线发射的种子光子的起源在喷流内。
英文摘要：
In this paper, by cross-correlating an archive sample of 542 extragalactic radio sources with the \emph{Fermi}-LAT Third Source Catalog(3FGL), we have compiled a sample of 80 $γ$-ray sources and 462 non-\emph{Fermi} sources with available core dominance parameter($R_{CD}$), core and extended radio luminosity; all the parameters are directly measured or derived from available data in the literature. We found that $R_{CD}$ have significant correlations with radio core luminosities, $γ$-ray luminosity and $γ$-ray flux respectively; the \emph{Fermi} sources have on average higher $R_{CD}$ than non-\emph{Fermi} sources. These results indicate that the \emph{Fermi} sources should be more compact, and beaming effect should play a crucial role for the detection of $γ$-ray emission. Moreover, our results also show \emph{Fermi} sources have systematically larger radio flux than non-\emph{Fermi} sources at fixed $R_{CD}$, indicating larger intrinsic radio flux in \emph{Fermi} sources. These results show a strong connection between radio and $γ$-ray flux for the present sample and indicate that the non-\emph{Fermi} sources is likely due to low beaming effect, and/or the low intrinsic $γ$-ray flux, support a scenario in the literature: a co-spatial origin of the activity for the radio and $γ$-ray emission, suggesting that the origin of the seed photons for the high-energy $γ$-ray emission is within the jet.
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