This article reviews our current understanding about $\gamma$-ray detected narrow-line Seyfert 1 ($\gamma$-NLSy1) galaxies. The detection with the Large Area Telescope onboard {\it Fermi}~Gamma-ray Space Telescope has provided the strongest evidence for the presence of closely aligned relativistic jet in these intriguing active galactic nuclei (AGN) and opened up a realm to explore the physical conditions needed to launch the jet in a different central engine and host galaxy environment than that is known for blazars. Promising results acquired from various multi-wavelength campaigns are converging to a scenario in which the $\gamma$-NLSy1 galaxies can be considered as `young' blazars. These enigmatic sources hold the key to unravel the jet triggering mechanism and evolution of the AGN phase of a galaxy, in general. As such, $\gamma$-NLSy1s should be considered as one of the top priority targets for next generation observational facilities.

中文翻译：

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伽马射线发射窄线赛弗特 1 星系：过去、现在和未来

本文回顾了我们目前对 $\gamma$ 射线探测到的窄线 Seyfert 1 ($\gamma$-NLSy1) 星系的理解。机载大面积望远镜{\it Fermi}~伽马射线太空望远镜的探测为这些有趣的活动星系核（AGN）中存在紧密排列的相对论喷流提供了最有力的证据，并开辟了一个探索物理的领域在不同于耀变体已知的中央引擎和宿主星系环境中发射喷流所需的条件。从各种多波长活动中获得的有希望的结果正在收敛到 $\gamma$-NLSy1 星系可以被视为“年轻”耀变体的情景。一般来说，这些神秘的来源是解开星系 AGN 阶段的喷射触发机制和演化的关键。因此，