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arXiv 1201.4950astro-ph.CO
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核星团是大质量黑洞的前兆吗?

Are nuclear star clusters the precursors of massive black holes?

Nadine Neumayer, C. Jakob Walcher

摘要:

我们提出了极晚型旋涡星系中黑洞质量的新上限。我们确认这类星系中存在质量小于10^6兆太阳能的黑洞(如果有的话)。我们还得到了新的上限核星团(NC)的质量与以前确定的黑洞质量的大质量星系。我们使用新推导的上限和文献汇编,研究低质量端的全球核关系。我们发现:(1)M_BH-σ关系在低质量时不能变平,而可能变陡。(2)相反,M_BH-M_bulge关系可以很好地变平。(3)M_BH-Sersic n关系能够解释低质量盘星系中黑洞质量的大散射。在M_BH-Sersic n关系中的异常值似乎是矮椭圆星系。当绘制M_BH与M_NC的关系图时,我们发现三种不同的区域:(a)核团主导的核,(b)过渡区,和(c)黑洞主导的核。这与图像一致,其中黑洞形成于具有非常低质量分数的核簇内。它们随后比核团簇增长得快得多,当M_BH/M_NC比增长到100以上时,核团簇被摧毁。因此,核星团可能是星系核中大质量黑洞的前兆。

英文摘要:

We present new upper limits for black hole masses in extremely late type spiral galaxies. We confirm that this class of galaxies has black holes with masses less than 10^6 Msolar, if any. We also derive new upper limits for nuclear star cluster (NC) masses in massive galaxies with previously determined black hole masses. We use the newly derived upper limits and a literature compilation to study the low mass end of the global-to-nucleus relations. We find the following (1) The M_BH-sigma relation cannot flatten at low masses, but may steepen. (2) The M_BH-M_bulge relation may well flatten in contrast. (3) The M_BH-Sersic n relation is able to account for the large scatter in black hole masses in low-mass disk galaxies. Outliers in the M_BH-Sersic n relation seem to be dwarf elliptical galaxies. When plotting M_BH versus M_NC we find three different regimes: (a) nuclear cluster dominated nuclei, (b) a transition region, and (c) black hole-dominated nuclei. This is consistent with the picture, in which black holes form inside nuclear clusters with a very low-mass fraction. They subsequently grow much faster than the nuclear cluster, destroying it when the ratio M_BH/M_NC grows above 100. Nuclear star clusters may thus be the precursors of massive black holes in galaxy nuclei.

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