标题： 中等质量黑洞的并购驱动增长：来自超亮X射线源哈勃空间望远镜成像的限制 显示英文标题

标题： Merger-Driven Growth of Intermediate-mass Black Holes: Constraints from Hubble Space Telescope Imaging of Hyper-luminous X-Ray Sources

摘要： 超亮X射线源（HLXs）是星系外的非核X射线源，其亮度超过恒星级致密天体吸积的理论极限。 许多HLX可能代表通过合并沉积在星系晕中的中等质量黑洞（IMBHs），围绕HLX的恒星核心特性为这一情景提供了强有力的约束。 因此，我们系统地构建了最大的HLX候选者样本，使用档案中的哈勃空间望远镜（HST）成像（24）进行首次对HLX恒星核心的统一种群研究，直至低质量。 根据其宿主星系红移，至少21个（88%）具有恒星核心质量≥10^7 Msun，因此与来自外部星系的超大质量黑洞吸积一致。 在样本的50%中，HST成像揭示了连接HLX与宿主星系的特征，强烈表明这些情况下不存在背景/前景污染的可能性。 假设活动星系核的质量比例关系，并考虑估计的污染比例为29%，我们的样本中多达~60%可能与IMBH有关。 与之前已知的HLX类似，X射线光度相对于其恒星核心质量系统性地升高，可能是由于合并驱动的吸积率增强。 最轻的恒星核心更倾向于出现在更大的核偏移处，并更有可能在其宿主星系晕中游荡。 HLX的星系占用分数为~10^-2，并具有强烈的质量反比依赖性。 多达三个HLX候选者（12%）可能与球状星团内的形成或极其明亮的X射线双星有关。 显示英文摘要

摘要： Hyper-luminous X-ray sources (HLXs) are extragalactic off-nuclear X-ray sources with luminosities exceeding the theoretical limit for accretion onto stellar-mass compact objects. Many HLXs may represent intermediate-mass black holes (IMBHs) deposited in galaxy halos through mergers, and properties of the stellar cores surrounding HLXs provide powerful constraints on this scenario. Therefore, we have systematically built the largest sample of HLX candidates with archival Hubble Space Telescope (HST) imaging (24) for the first uniform population study of HLX stellar cores down to low masses. Based on their host galaxy redshifts, at least 21 (88%) have stellar core masses >=10^7 Msun and hence are consistent with accretion onto massive black holes from external galaxies. In 50% of the sample, the HST imaging reveals features connecting the HLXs with their host galaxies, strongly suggesting against the background/foreground contaminant possibility in these cases. Assuming a mass scaling relation for active galactic nuclei and accounting for an estimated contamination fraction of 29%, up to ~60% of our sample may be associated with IMBHs. Similar to previously known HLXs, the X-ray luminosities are systematically elevated relative to their stellar core masses, possibly from merger-driven accretion rate enhancements. The least massive stellar cores are preferentially found at larger nuclear offsets and are more likely to remain wandering in their host galaxy halos. The HLX galaxy occupation fraction is ~10^-2 and has a strong inverse mass dependence. Up to three of the HLX candidates (12%) are potentially consistent with formation within globular clusters or with exceptionally luminous X-ray binaries.