We present a study of the extended radio emission in a sample of 8434 low-redshift (z 0.35) broad-line active galactic nuclei (AGNs) from the Sloan Digital Sky Survey. To calculate the jet and lobe contributions to the total radio luminosity, we have taken the 846 radio core sources detected in our previous study of this sample and performed a systematic search in the FIRST database for extended radio emission that is likely associated with the optical counterparts. We found that 51 out of 846 radio core sources have extended emission (4'' from the optical AGN) that is positively associated with the AGN, and we have identified an additional 12 AGNs with extended radio emission but no detectable radio core emission. Among these 63 AGNs, we found 6 giant radio galaxies, with projected emission exceeding 750 kpc in length, and several other AGNs with unusual radio morphologies also seen in higher redshift surveys. The optical spectra of many of the extended sources are similar to those of typical broad-line radio galaxy spectra, having broad Hα emission lines with boxy profiles and large M BH. With extended emission taken into account, we find strong evidence for a bimodal distribution in the radio-loudness parameter (≡νradio L radio/νopt L opt), where the lower radio luminosity core-only sources appear as a population separate from the extended sources, with a dividing line at log() ≈1.75. This dividing line ensures that these are indeed the most radio-loud AGNs, which may have different or extreme physical conditions in their central engines when compared to the more numerous radio-quiet AGNs.
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机译：我们对斯隆数字天空调查的8434个低红移（z <0.35）宽线活动银河核（AGN）样本进行了扩展无线电发射的研究。为了计算射流和波瓣对总无线电发光度的贡献，我们采用了我们先前对该样本的研究中检测到的846个无线电核心源，并在FIRST数据库中进行了系统搜索以寻找可能与光学对等物相关的扩展无线电发射。我们发现846个无线电核心源中有51个具有与AGN正相关的扩展发射（来自光学AGN的发射> 4英寸），并且我们确定了另外12个AGN具有扩展无线电发射但没有可检测到的无线电核心发射。在这63个AGN中，我们发现了6个巨大的无线电星系，预计发射的长度超过750 kpc，在更高的红移调查中也发现了其他几种具有异常无线电形态的AGN。许多扩展源的光谱类似于典型的宽谱线射电星系光谱，具有宽的Hα发射线，具有箱形轮廓和大的M BH。考虑到扩展发射，我们找到了无线电响度参数（≡νradioL radio /νoptL opt）中双峰分布的有力证据，其中较低的仅发光度核心的源与扩展源分开出现，在log（）≈1.75处有分隔线。这条分界线确保了这些确实是无线电噪声最大的AGN，与数量众多的无线电静音AGN相比，它们的中央引擎可能具有不同或极端的物理条件。
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