内部辐射反馈触发无金属原子冷却晕中的整体坍缩和直接坍缩黑洞形成
Internal Radiative Feedback Triggers Global Collapse and Direct-Collapse Black Hole Formation in Metal-free Atomic-Cooling Haloes
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中文总结 AI 辅助
本研究通过宇宙学辐射流体模拟发现，无金属原子冷却晕中的内部恒星反馈可触发整体坍缩，形成超大质量恒星并进而产生直接坍缩黑洞，放宽了对外部远紫外辐射场的要求。
中文摘要 AI 辅助
超大质量恒星（SMSs）坍缩形成重种子黑洞是超大质量黑洞（SMBHs）形成的一条有前景的路径。然而，在传统的直接坍缩场景中，SMS的形成需要极其强的外部远紫外（FUV）辐射场来抑制H$_2$冷却和碎裂。在这里，我们使用宇宙学辐射流体动力学模拟表明，即使在亚临界的FUV背景下（$J_{21}=1$-$10^2$），SMSs也可以在无金属原子冷却晕中形成。我们跟踪了恒星形成开始后约$1$-$2~{\rm Myr}$的演化，包括晕内形成的恒星发出的FUV和电离辐射。恒星形成经历了一个典型的两阶段演化过程。最初，H$_2$冷却诱导碎裂和普通Pop III恒星的形成。这些恒星发出的内部FUV辐射随后光解离H$_2$并抑制进一步的碎裂，而周围温暖的气体储库在自引力作用下收缩，并通过原子冷却经历整体坍缩。这种坍缩驱动了约$0.1$-$1~{\rm M_\odot~yr^{-1}}$的流入速率，并产生了快速吸积的原恒星，在模拟结束时达到约$2$-$6\times10^4~{\rm M_\odot}$。由于快速吸积仍在进行，这些天体预计将增长到约$10^5~{\rm M_\odot}$的SMSs，然后形成直接坍缩黑洞（DCBHs）。整体坍缩伴随着成团恒星形成，在SMSs周围产生一个紧凑的、顶部重的恒星系统。估计的DCBH丰度$n_{\rm DCBH}\sim10^{-3}$-$10^{-2}~{\rm cMpc^{-3}}$，足够高，为Little Red Dots和当今的SMBHs提供了一个合理的祖先群体。我们的结果表明，内部恒星反馈可以触发而非阻止SMS的形成，大大放宽了重种子形成对外部FUV的要求。
英文摘要
The formation of heavy seed black holes from the collapse of supermassive stars (SMSs) is a promising pathway to the supermassive black holes (SMBHs). In the conventional direct-collapse scenario, however, SMS formation requires an extremely strong external far-ultraviolet (FUV) field to suppress H$_2$ cooling and fragmentation. Here, we use cosmological radiation-hydrodynamic simulations to show that SMSs can form in metal-free atomic-cooling haloes even under subcritical FUV backgrounds with $J_{21}=1$-$10^2$. We follow the evolution for $\sim1$-$2~{\rm Myr}$ after the onset of star formation, including FUV and ionizing radiation from stars formed within the halo. Star formation proceeds through a characteristic two-stage evolution. H$_2$ cooling initially induces fragmentation and the formation of ordinary Pop III stars. Internal FUV radiation from these stars then photodissociates H$_2$ and suppresses further fragmentation, while the surrounding warm gas reservoir contracts under self-gravity and undergoes global collapse through atomic cooling. This collapse drives inflow rates of $\sim0.1$-$1~{\rm M_\odot~yr^{-1}}$ and produces rapidly accreting protostars that reach $\sim2$-$6\times10^4~{\rm M_\odot}$ by the simulations end. Since rapid accretion is still ongoing, these objects are expected to grow to $\sim10^5~{\rm M_\odot}$ SMSs and then form direct-collapse black holes (DCBHs). The global collapse is accompanied by clustered star formation, producing a compact, top-heavy stellar system around the SMSs. The estimated DCBH abundance, $n_{\rm DCBH}\sim10^{-3}$-$10^{-2}~{\rm cMpc^{-3}}$, is high enough to provide a plausible progenitor population for Little Red Dots and present-day SMBHs. Our results demonstrate that internal stellar feedback can trigger, rather than prevent, SMS formation, substantially relaxing the external FUV requirement for heavy-seed formation.
发表机构
- Astronomical Institute, Graduate School of Science, Tohoku University（东北大学理学研究科天体物理研究所）
- Max-Planck-Institut fur Astrophysik（马克斯·普朗克天体物理学研究所）
- Dipartimento di Fisica, “Sapienza” Università di Roma（罗马第一大学物理系）
- Sapienza School for Advanced Studies（萨皮恩扎高等研究院）
- INFN, Sezione Roma1, Dipartimento di Fisica, “Sapienza” Università di Roma（罗马第一大学物理系意大利国家核物理研究所）
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