The most elusive and extreme subclass of active galactic nuclei (AGNs), known as BL Lac objects, shows features that can only be explained as the result of relativistic effects occurring in jets pointing at a small angle with respect to the line of sight. A longstanding issue is the identification of the BL Lac parent population with jets oriented at larger angles. According to the “unification scenario” of AGNs, radio galaxies with low luminosity and an edge-darkened radio morphology are the most promising candidate parent population of BL Lacs. Here we compare the large-scale environment, an orientation-independent property, of well-defined samples of BL Lacs with samples of radio galaxies all lying in the local universe. Our study reveals that BL Lacs and radio galaxies live in significantly different environments, challenging predictions of the unification scenario. We propose a solution to this problem proving that large-scale environments of BL Lacs are statistically consis...

中文翻译：

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龙之巢穴：BL Lac对象的大规模环境

被称为BL Lac对象的活动银河系原子核（AGN）最难以捉摸和最极端的子类显示的特征只能解释为相对于视线指向较小角度的喷流中发生的相对论效应的结果。长期存在的问题是使用较大角度的射流识别BL Lac父母群体。根据AGN的“统一方案”，低亮度的无线电星系和边缘变暗的无线电形态是BL Lacs最有希望的候选亲本种群。在这里，我们将定义明确的BL Lacs样本与位于整个宇宙中的射电星系样本的大规模环境（一种与方向无关的属性）进行了比较。我们的研究表明，BL Lacs和射电星系生活在截然不同的环境中，统一场景的具有挑战性的预测。我们提出了一个解决方案，证明BL Lacs的大规模环境在统计上是连续的...