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arXiv 2406.13005astro-ph.GA
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z=4.3 时 SPT2349–56 原星团中超大质量黑洞的快速增长

Fast SMBH growth in the SPT2349--56 protocluster at $z=4.3$

Fabio Vito, William N. Brandt, Andrea Comastri, Roberto Gilli, Rob J. Ivison, Giorgio Lanzuisi, Bret D. Lehmer, Ivan E. Lopez, Paolo Tozzi, Cristian Vignali

AI总结:

研究利用 Chandra 观测 z=4.3 的富气体原星团 SPT2349-56,发现约10%的 DSFG 承载遮蔽 AGN,且高光度 AGN 触发率较场环境高3–5个数量级,表明此类环境促进 SMBH 快速增长。

摘要:

z>2 的原星团是富含气体的区域,具有高恒星形成活动的特征。人们认为,增强原星团中恒星形成的那些相同物理性质,也会促进超大质量黑洞(SMBH)的增长。我们旨在通过 Chandra(200 ks)观测探测 SPT2349-56 的活动星系核(AGN)含量,并将结果与场环境进行比较,以检验这一情景;SPT2349-56 是 z=4.3 处一个大质量、富含气体且高恒星形成率的原星团核心,最初作为尘埃恒星形成星系(DSFG)的过密区被发现。我们探测到两个原星团成员,对应 DSFG 中约 10% 的 AGN 比例。该数值与 z=2–4 的其他原星团一致,但高于场环境中 DSFG 的 AGN 发生率。两个 AGN 都是严重遮蔽源,位于恒星质量约为 3×10^10 M⊙ 的恒星形成星系中。我们估计宿主星系中的星际介质(ISM)可对核区遮蔽作出显著贡献。两个 AGN 中有一个具有高光度(L_X=2×10^45 erg s^-1)且为康普顿厚(N_H=2×10^24 cm^-2),其能量很可能来自一个 M_BH>6×10^8 M⊙ 的 SMBH。其高吸积率表明,它正处于高效增长阶段,而这正是解释局域星系团中心存在极端大质量 SMBH 所需要的阶段。综合考虑 SPT2349-56 与 z=4 处类似原星团 DRC,我们发现,相对于场环境,z≈4 时富含气体的原星团核心会使高光度(log(L_X/(erg s^-1))=45–46)AGN 的触发增强 3–5 个数量级。结果表明,高红移富含气体的原星团会促进 SMBH 增长,这可能影响后续结构演化,因此它们是完整理解环境与星系演化关系的关键科学目标。

英文摘要:

Protoclusters at $z>2$ are gas-rich regions characterized by high star-formation activity. The same physical properties that enhance star formation in protoclusters are also thought to boost the growth of SMBHs. We aim to test this scenario by probing the AGN content of SPT2349-56, a massive, gas-rich, and highly star-forming protocluster core at $z=4.3$ discovered as an overdensity of DSFGs, via Chandra (200 ks) observations, and comparing the results with the field environment. We detected two protocluster members, corresponding to an AGN fraction among DSFGs of $\approx10\%$. This value is consistent with other protoclusters at $z=2-4$, but higher than the AGN incidence among DSFGs in the field environment. Both AGN are heavily obscured sources and hosted in star-forming galaxies with $\approx3\times10^{10}\,\mathrm{M_\odot}$ stellar masses. We estimate that the ISM in the host galaxies can contribute significantly to the nuclear obscuration. One of the two AGN is highly luminous ($L_X=2\times10^{45}\,\mathrm{erg\,s^{-1}}$) and Compton-thick ($N_H=2\times10^{24}\,\mathrm{cm^{-2}}$), and likely powered by a $M_{BH}>6\times10^8\,\mathrm{M_\odot}$ SMBH. Its high accretion rate suggests that it is in the phase of efficient growth required to explain the presence of extremely massive SMBHs in the centers of local galaxy clusters. Considering SPT2349-56 and DRC, a similar protocuster at $z=4$, we find that gas-rich protocluster cores at $z\approx4$ enhance the triggering of luminous (log$\frac{L_X}{\mathrm{erg\,s^{-1}}}=45-46$) AGN by 3-5 orders of magnitude with respect to the field environment. Our results indicate that gas-rich protoclusters at high redshift boost the growth of SMBHs, which will likely impact the subsequent evolution of the structures, and thus represent key science targets to obtain a complete understanding of the relation between environment and galaxy evolution.

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