The discovery in 2008 of high-energy gamma-rays from Narrow-Line Seyfert 1 Galaxies (NLS1s) made it clear that there were active galactic nuclei (AGN) other than blazars and radio galaxies that can eject powerful relativistic jets. In addition to NLS1s, the great performance of the Fermi Large Area Telescope made it possible to discover MeV-GeV photons emitted from more classes of AGN, like Seyferts, Compact Steep Spectrum Gigahertz Peaked Sources (CSS/GPS), and disk-hosted radio galaxies. Although observations indicate a variety of objects, their physical characteristics point to a central engine powered by a relatively small-mass black hole (but, obviously, there are interpretations against this view). This essay critically reviews the literature published on these topics during the last eight years and analyzes the perspectives for the forthcoming years.

中文翻译：

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喷射窄线赛弗1星系公司：我们站在哪里？

Narrow-Line Seyfert 1星系（NLS1s）在2008年发现了高能伽玛射线，这清楚地表明，除了天体和射电星系以外，还有活跃的银河核（AGN）可以发射强大的相对论射流。除了NLS1，费米的出色性能借助大面积望远镜，可以发现从更多种类的AGN（例如赛弗特，紧凑型陡峭频谱千兆赫兹峰值源（CSS / GPS）和磁盘托管的无线电星系）发出的MeV-GeV光子。尽管观察表明有各种各样的物体，但它们的物理特性指向由相对较小质量的黑洞提供动力的中央发动机（但显然，对此观点有种种解释）。本文对过去八年中有关这些主题的文献进行了批判性的回顾，并分析了未来几年的观点。