A Population of Bona Fide Intermediate-mass Black Holes Identified as Low-luminosity Active Galactic Nuclei
A Population of Bona Fide Intermediate-mass Black Holes Identified as Low-luminosity Active Galactic Nuclei
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DOI：
10.3847/1538-4357/aad184
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发表时间：
2018-05
期刊：
影响因子：
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通讯作者：
I. Chilingarian;I. Katkov;I. Zolotukhin;Kirill A. Grishin;Y. Beletsky;K. Boutsia;D. Osip
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文献类型：
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作者：
I. Chilingarian;I. Katkov;I. Zolotukhin;Kirill A. Grishin;Y. Beletsky;K. Boutsia;D. Osip
几乎每个大质量星系的核心都有一个超大质量黑洞（SMBH）。超大质量黑洞的质量是数百万到数十亿太阳质量，它们与其宿主星系的椭球体的特性相关。虽然超大质量黑洞的生长通道、合并和气体吸积已经很成熟，但它们的起源仍然不确定：它们可能来自早期宇宙中气体云直接塌缩形成的巨大“种子”（105-106 M⊙），也可能来自较小的（100 M⊙）黑洞，即第一颗恒星的最终产物。后一个通道会留下大量中等质量的黑洞（IMBH，102-105 M⊙）。尽管已经确定了许多 IMBH 候选者，但没有一个被认为是最终的；因此，它们的存在仍然存在争议。通过在广域巡天中进行数据挖掘，并对档案和后续光谱进行专门分析，我们确定了 305 个 IMBH 候选恒星的样本，其质量为 3 × 10 4 M ⊙ < M BH < 2 × 10 5 M ⊙ ，它们位于星系中心，正在吸积气体，从而产生 I 型活动星系核 (AGN) 的特征特征。我们通过检测来自吸积盘的 X 射线发射，确认了 10 个源（包括五个先前已知的天体，验证了我们的方法）的 AGN 性质，从而定义了星系核中第一个真正的 IMBH 样本。所有 IMBH 宿主星系都拥有小型核球，并且位于 M BH – M 核球标度关系的低质量延伸部分，这表明它们在其一生中经历过的重大合并肯定是很少的（如果有的话）。核中等质量黑洞的存在本身就支持了大质量黑洞形成的恒星质量种子情景。
Nearly every massive galaxy harbors a supermassive black hole (SMBH) in its nucleus. SMBH masses are millions to billions of solar mass, and they correlate with properties of spheroids of their host galaxies. While the SMBH growth channels, mergers, and gas accretion are well established, their origin remains uncertain: they could have emerged either from massive “seeds” (105–106 M⊙) formed by direct collapse of gas clouds in the early universe or from smaller (100 M⊙) BHs, end products of first stars. The latter channel would leave behind numerous intermediate-mass BHs (IMBHs, 102–105 M⊙). Although many IMBH candidates have been identified, none are accepted as definitive; thus, their very existence is still debated. Using data mining in wide-field sky surveys and applying dedicated analysis to archival and follow-up optical spectra, we identified a sample of 305 IMBH candidates having masses 3 × 10 4 M ⊙ < M BH < 2 × 10 5 M ⊙ , which reside in galaxy centers and are accreting gas that creates characteristic signatures of a type I active galactic nucleus (AGN). We confirmed the AGN nature of 10 sources (including five previously known objects that validate our method) by detecting the X-ray emission from their accretion disks, thus defining the first bona fide sample of IMBHs in galactic nuclei. All IMBH host galaxies possess small bulges and sit on the low-mass extension of the M BH – M bulge scaling relation, suggesting that they must have experienced very few if any major mergers over their lifetime. The very existence of nuclear IMBHs supports the stellar-mass seed scenario of the massive BH formation.