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arXiv 1405.6743astro-ph.GA
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反馈调节的超大质量黑洞种子形成

Feedback-regulated Super Massive Black Hole Seed Formation

Mark Dijkstra, Andrea Ferrara, Andrei Mesinger

摘要:

高红移超大质量黑洞种子的性质是宇宙学中的一个关键问题。直接坍缩黑洞(DCBH),形成在原始的,原子线冷却晕,照明莱曼-沃纳(LW)紫外线通量超过临界阈值J_crit,代表了一个有吸引力的可能性。我们研究在宇宙演化过程中何时何地满足这些条件。对于LW强度J_LW,我们考虑了与恒星形成星系附近背景值的偏离。对于原始晕部分,我们考虑了(i)超新星驱动的外流,以及(ii)来自祖先晕的固有污染。我们估算了DCBH形成点的丰度n_DCBH(z),发现它随着宇宙时间的增加而增加,从n_DCBH(z=20)~ 1 e-12 - 1 e-7 cMpc^-3增加到n_DCBH(z=10)~ 1 e-10 - 1 e-5 cMpc^-3。我们的分析表明,星系风可能具有重要的作用,它可以将预测的n_DCBH抑制几个数量级,并导致DCBH的形成优先发生在紫外最亮(M_UV ~ -22 ~-20)的恒星形成星系周围。我们的分析进一步强调了这些预测对(i)LW光子的逃逸分数,(ii)J_crit和(iii)银河系外流处方的依赖性。

英文摘要:

The nature of the seeds of high-redshift supermassive black holes (SMBHs) is a key question in cosmology. Direct collapse black holes (DCBH) that form in pristine, atomic-line cooling halos, illuminated by a Lyman-Werner (LW) UV flux exceeding a critical threshold J_crit, represent an attractive possibility. We investigate when and where these conditions are met during cosmic evolution. For the LW intensity, J_LW, we account for departures from the background value in close proximity to star forming galaxies. For the pristine halo fraction, we account for both (i) supernova driven outflows, and (ii) the inherent pollution from progenitor halos. We estimate the abundance of DCBH formation sites, n_DCBH(z), and find that it increases with cosmic time from n_DCBH(z=20) ~ 1e-12 -1e-7 cMpc^-3 to n_DCBH(z=10) ~ 1e-10 - 1e-5 cMpc^-3. Our analysis shows the possible importance of galactic winds, which can suppress the predicted n_DCBH by several orders of magnitude, and cause DCBH formation to preferentially occur around the UV-brightest (M_UV ~ -22 to -20) star forming galaxies. Our analysis further highlights the dependence of these predictions on (i) the escape fraction of LW photons, (ii) J_crit, and (iii) the galactic outflow prescription.

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