极端潮汐剥离可能解释Leo I中的超大质量黑洞：概念验证
Extreme Tidal Stripping May Explain the Overmassive Black Hole in Leo I: a Proof of Concept
AI总结：
本文从动力学角度提出，Leo I矮星系中心的超大质量黑洞偏离标准关系可能是因为其前身星系在银河系内经历了一两次近距离穿过导致的极端潮汐剥离，解析模型与N体模拟表明其恒星质量损失可达90%，且该潮汐流的证据可能存在于Gaia数据中。
摘要：
最近的一项研究在Leo I（银河系最遥远的矮椭球星系）中心发现了质量约为$3 \times 10^{6} \\, \rm M_\odot$的超大质量黑洞的动力学证据。这个黑洞的质量与银河系的Sgr A*相当，使得该系统在标准的$M_\bullet-M_{\star}$关系之上超过$2$个数量级。我们从动力学角度研究了这种可能性：Leo I的恒星系统最初质量要大得多，因此更接近该关系。在银河系位力半径内一次或两次近距离穿过造成的极端潮汐破坏，可能剥离了其大部分恒星质量。一个简单的解析模型表明，Leo I的前身星系在单次近心点经过时可能经历了$32\\% - 57\\%$的质量损失，具体取决于恒星速度弥散的估计值。如果近心点位于当前轨道重构所允许的最小距离处，该质量损失比例将增至$66\\% - 78\\%$。详细的N体模拟显示，经过最多两次穿越后，质量损失可达约$90\\%$，其近心点距离同样与Gaia数据所允许的最小值相容。尽管Leo I的性质存在非常大的不确定性，我们在误差因子$< 2$的范围内重现了其当前位置和速度弥散，以及$1$ kpc内最终的恒星质量（约$5\times 10^6 \\, \rm M_\odot$）。最新的潮汐流朝向我们指向Leo I的视线方向，使其难以被探测到。这种极端潮汐破坏事件的证据可能以延伸的潮汐流形式存在于当前的Gaia数据中。
英文摘要：
A recent study found dynamical evidence of a supermassive black hole of $\sim 3 \times 10^{6} \, \rm M_\odot$ at the center of Leo I, the most distant dwarf spheroidal galaxy of the Milky Way. This black hole, comparable in mass to the Milky Way's Sgr A*, places the system $>2$ orders of magnitude above the standard $M_\bullet-M_{\star}$ relation. We investigate the possibility, from a dynamical standpoint, that Leo I's stellar system was originally much more massive and, thus, closer to the relation. Extreme tidal disruption from one or two close passages within the Milky Way's virial radius could have removed most of its stellar mass. A simple analytical model suggests that the progenitor of Leo I could have experienced a mass loss in the range of $32\% - 57\%$ from a single pericenter passage, depending on the stellar velocity dispersion estimate. This mass loss percentage increases to the range $66\% - 78\%$ if the pericenter occurs at the minimum distance allowed by current orbital reconstructions. Detailed N-body simulations show that the mass loss could reach $\sim 90\%$ with up to two passages, again with pericenter distances compatible with the minimum value allowed by Gaia data. Despite very significant uncertainties in the properties of Leo I, we reproduce its current position and velocity dispersion, as well as the final stellar mass enclosed in $1$ kpc ($\sim 5\times 10^6 \, \rm M_\odot$) within a factor $< 2$. The most recent tidal stream is directed along our line of sight toward Leo I, making it difficult to detect. Evidence from this extreme tidal disruption event could be present in current Gaia data in the form of extended tidal streams.
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