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The central black hole in the dwarf spheroidal galaxy Leo I: Not supermassive, at most an intermediate-mass candidate
Astronomy & Astrophysics ( IF 6.5 ) Pub Date : 2024-04-17 , DOI: 10.1051/0004-6361/202449620
R. Pascale , C. Nipoti , F. Calura , A. Della Croce

It has recently been claimed that a surprisingly massive black hole (BH) is present in the core of the dwarf spheroidal galaxy (dSph) Leo I. This finding, based on integral field spectroscopy, challenges the typical expectation that dSphs host intermediate-mass BHs since such a BH would be classified as supermassive. Indeed, the analysis points toward Leo I harboring a BH with a lower mass limit exceeding a few 106M at 1σ, and the no-BH case excluded at 95% significance. Such a mass, which is comparable to the entire stellar mass of the galaxy, makes Leo I a unique system that warrants further investigation. Using equilibrium models based on distribution functions that depend on actions f(J) coupled with the same integral field spectroscopy data and an extensive exploration of a very large parameter space, we demonstrate, within a comprehensive Bayesian model–data comparison framework, that the posterior on the BH mass is flat toward the low-mass end and, thus, that the kinematics of the central galaxy region only imposes an upper limit on the BH mass of few 105M (at 3σ). Such an upper limit indicates that the putative BH of Leo I is at most an intermediate-mass BH, and it is also in line with formation scenarios and expectations from scaling relations at the mass regime of dwarf galaxies.

中文翻译:

矮椭球星系Leo I的中心黑洞:不是超大质量,最多是中等质量候选者

最近有人声称,矮椭球星系 (dSph) Leo I 的核心存在一个质量惊人的黑洞 (BH)。这一基于积分场光谱的发现挑战了 dSphs 拥有中等质量 BH 的典型预期因为这样的黑洞将被归类为超大质量。事实上,分析表明 Leo I 拥有一个在 1 σ处质量下限超过几个 10 6 M ⊙的 BH ,并且在 95% 的显着性下排除了无 BH 的情况。这样的质量可与银河系的整个恒星质量相媲美,使狮子座一号成为一个值得进一步研究的独特系统。使用基于取决于作用f ( J ) 的分布函数的平衡模型,加上相同的积分场光谱数据以及对非常大的参数空间的广泛探索,我们在综合贝叶斯模型-数据比较框架内证明,后验BH 质量向低质量端平坦,因此,中央星系区域的运动学仅对 BH 质量施加上限,约为 10 5 M (在 3 σ处)。这样的上限表明,Leo I 的推定 BH 至多是中等质量的 BH,也符合矮星系质量体系标度关系的形成情景和预期。
更新日期:2024-04-17
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