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arXiv 1910.08554astro-ph.GA
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大质量黑洞种子周围的诱导无金属恒星形成

Induced metal-free star formation around a massive black hole seed

Aycin Aykutalp, Kirk S. S. Barrow, John H. Wise, Jarrett L. Johnson

摘要:

大质量黑洞的直接形成是最早观测到的超大质量黑洞的潜在播种机制。我们研究了大质量黑洞种子的存在如何影响其前星系宿主晕的电离和热状态以及随后的恒星形成。我们发现,它的X射线辐射电离和加热介质,增强$\rm{H}_2$形成屏蔽区域,在核区域内的跨度为一百万年。增强的分子冷却触发了$\sim 10^4~{\rm M}_\odot$无金属星团的形成,在一次事件中恒星形成效率为$\sim 0.1\%$。恒星的形成发生在H II区域的边缘,该区域被X射线部分电离,因此初始大小取决于黑洞的性质和周围环境。模拟的无金属星系的初始半光半径为$\sim 10$ pc,但由于其诞生云的向外速度,在1000万年后膨胀到$\sim 50$ pc。超新星反馈然后熄灭任何进一步的恒星形成数千万年,允许大质量黑洞主宰光谱一旦大质量无金属恒星死亡。

英文摘要:

The direct formation of a massive black hole is a potential seeding mechanism of the earliest observed supermassive black holes. We investigate how the existence of a massive black hole seed impacts the ionization and thermal state of its pre-galactic host halo and subsequent star formation. We show that its X-ray radiation ionizes and heats the medium, enhancing $\rm{H}_2$ formation in shielded regions, within the nuclear region in the span of a million years. The enhanced molecular cooling triggers the formation of a $\sim 10^4~{\rm M}_\odot$ metal-free stellar cluster at a star formation efficiency of $\sim 0.1\%$ in a single event. Star formation occurs near the edges of the H II region that is partially ionized by X-rays, thus the initial size depends on the black hole properties and surrounding environment. The simulated metal-free galaxy has an initial half-light radius of $\sim 10$ pc but expands to $\sim 50$ pc after 10 million years because of the outward velocities of their birth clouds. Supernova feedback then quenches any further star formation for tens of millions of years, allowing the massive black hole to dominate the spectrum once the massive metal-free stars die.

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