arXiv 1807.047682018-07astro-ph.GAastro-ph.COastro-ph.HE

高红移矮星系中中等质量黑洞的生长和反馈

Intermediate-Mass Black Hole Growth and Feedback in Dwarf Galaxies at High Redshifts

Paramita Barai, Elisabete M. de Gouveia Dal Pino

备注：: 18 pages, 9 figures, 2 tables. Version accepted for publication in the MNRAS
DOI：: 10.1093/mnras/stz1616

摘要：

与恒星质量和超大质量黑洞相比，中等质量黑洞（IMBH：质量在$100 - 10^{6} M_{\odot}$之间）历史上是一个难以捉摸的群体。最近，IMBH已经开始在低质量星系的中心被观测到。我们对$(2 h^{-1} ~ {\rm Mpc})^3$共动盒进行了宇宙学流体动力学模拟，并研究了矮星系中中心IMBH的生长和反馈。最早的黑洞出现在$z \sim 18 - 25$，然后通过吸积气体和与其他黑洞合并而增长。我们发现，从$10^{2} M_{\odot}$开始，当BH被播种在质量小于$4 \times 10^{7} M_{\odot}$的晕中时，通过$z = 5$建立几个$\times 10^{5} - 10^{6} M_{\odot}$的IMBH是可能的。BH的吸积速率随时间增加，对于大质量的IMBH，吸积速率达到$\dot{M}_{\rm BH} = (0.2 - 0.8) \dot{M}_{\rm Edd}$，吸积速率为$z = 4$。恒星质量（恒星质量$10^{5} - 10^{8} M_{\odot}$）的恒星形成率密度（SFRD）演化在$z = 4 - 6$之间有一个峰值平台。恒星的形成在$z = 9 - 4$之间被淬灭。当BH已经增长到$10^5 M_{\odot}$的几倍时，SFRD被降低高达$3$的因子。即使在存在更强的SN驱动的质量喷射，BH继续成长为$z \sim 6$，维持气体流入驱动星系合并和相互作用在宇宙学环境。基于数值模拟结果，我们的结论支持$z = 5 - 8$富气DG中IMBH的早期反馈可能解决$Λ$ CDM宇宙学情景中DG质量范围内的几个异常的情况（Silk 2017）。我们的研究结果表明，在DG中心的IMBH的增长速度比他们的宿主星系在早期宇宙，和由此产生的BH反馈把DG和BH休眠。

英文摘要：

Intermediate-mass black holes (IMBHs: masses between $100 - 10^{6} M_{\odot}$) historically comprise of an elusive population compared to stellar-mass and supermassive BHs. Recently IMBHs have started to be observed at the centers of low-mass galaxies. We perform cosmological hydrodynamical simulations of $(2 h^{-1} ~ {\rm Mpc})^3$ comoving boxes and investigate the growth and feedback of central IMBHs in dwarf galaxies (DGs). The earliest BHs appear at $z \sim 18 - 25$, and grow thereafter by accreting gas and by merger with other BHs. We find that, starting from $10^{2} M_{\odot}$, it is possible to build up IMBHs of a few$\times 10^{5} - 10^{6} M_{\odot}$ by $z = 5$, when the BHs are seeded in halos less massive than $4 \times 10^{7} M_{\odot}$. The BH accretion rates increase with time, and reaches $\dot{M}_{\rm BH} = (0.2 - 0.8) \dot{M}_{\rm Edd}$ for the massive IMBHs by $z = 4$. The star formation rate density (SFRD) evolution of the DGs (stellar mass $10^{5} - 10^{8} M_{\odot}$) has a peak plateau between $z = 4 - 6$. Star formation is quenched between $z = 9 - 4$. The SFRD is reduced by factors up to $3$, when the BHs have grown to a few times $10^5 M_{\odot}$. Even in the presence of stronger SN-driven mass ejection, the BHs continue to grow up to $z \sim 6$, sustained by gas inflows driven by galaxy mergers and interactions in a cosmological environment. Our conclusions, based on numerical simulation results, support the scenario that early feedback from IMBHs in gas-rich DGs at $z = 5 - 8$ can potentially solve several anomalies in the DG mass range within the concordance $Λ$CDM cosmological scenario (Silk 2017). Our results suggest that IMBHs at DG centers grow faster than their host galaxies in the early Universe, and the resulting BH feedback turns the DGs and the BHs dormant.

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