NGC 3998是一个位于大熊座的透鏡狀星系,1789年4月14日由威廉·赫歇爾发现[5],距离地球4500万光年[2][6]。NGC 3998有一个活动星系核,属于LINER星系[6]。
- ^ 1.0 1.1 1.2 1.3 1.4 1.5 Results for object NGC 3998 (NGC 3998). NASA/IPAC Extragalactic Database. California Institute of Technology. [2021-04-25]. (原始内容存档于2022-06-28).
- ^ 2.0 2.1 Walsh, Jonelle L.; Van Den Bosch, Remco C. E.; Barth, Aaron J.; Sarzi, Marc. A Stellar Dynamical Mass Measurement of the Black Hole in NGC 3998 from Keck Adaptive Optics Observations. The Astrophysical Journal. 2012, 753 (1): 79. Bibcode:2012ApJ...753...79W. S2CID 16506695. arXiv:1205.0816 . doi:10.1088/0004-637X/753/1/79.
- ^ Véron-Cetty, M.-P.; Véron, P. A catalogue of quasars and active nuclei. Astronomy and Astrophysics 13th. 2010, 518: A10. Bibcode:2010A&A...518A..10V. doi:10.1051/0004-6361/201014188 .
- ^ NGC 3998. SIMBAD. 斯特拉斯堡天文資料中心. [2021-04-25].
- ^ 5.0 5.1 Seligman, Courtney. New General Catalogue objects: NGC 3950 - 3999. cseligman.com. [2021-04-25]. (原始内容存档于2019-02-18).
- ^ 6.0 6.1 Frank, Bradley S.; Morganti, Raffaella; Oosterloo, Tom; Nyland, Kristina; Serra, Paolo. A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: The story of NGC 3998. Astronomy & Astrophysics. 2016, 592: A94. Bibcode:2016A&A...592A..94F. S2CID 73593876. arXiv:1605.03873 . doi:10.1051/0004-6361/201628282.