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arXiv 1707.03014astro-ph.GAastro-ph.COastro-ph.HE
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在$z \geq 6$的类星体流出：对宿主星系的影响

Quasar outflows at $z \geq 6$: the impact on the host galaxies

Paramita Barai, Simona Gallerani, Andrea Pallottini, Andrea Ferrara, Alessandro Marconi, Claudia Cicone, Roberto Maiolino, Stefano Carniani

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17 pages (excluding references and appendix), 11 figures, Submitted
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摘要：

我们调查类星体流出在$z \geq 6$进行放大宇宙流体动力学模拟。通过使用SPH代码GADGET-3，我们在$(500 ~ {\rm Mpc})^3$共动体积内的$z = 6$处的$2 \times 10^{12} M_{\odot}$晕周围放大$2 R_{200}$区域。我们比较我们的活动星系核运行的控制模拟，其中只考虑恒星/SN反馈的结果。在$10^{9} M_{\odot}$晕的中心播种$10^5 M_{\odot}$ BH，我们发现以下结果。黑洞在PDMATHAMT上以爱丁顿速率吸积气体。在$z = 6$，我们最大质量的BH已经增长到$M_{\rm BH} = 4 \times 10^9 M_{\odot}$。快速（$v_{r} > 1000$ km/s），强大（$\dot{M}_{\rm out} \sim 2000 M_{\odot}$ /yr）的激波加热的低密度气体外流在$z \sim 7$形成，并传播到数百kpc。恒星形成在$z = 8 - 6$上被淬灭，总SFR（星系中心附近的SFR表面密度）减少了$5$（$1000$）的因子。我们分析了多种物理过程的相对贡献：（i）破坏宇宙的间接冷气体流入，（ii）降低中心气体密度，（iii）喷射气体到星系外，并发现活动星系核反馈在$z = 6$有以下影响。流入气体质量分数减少$\sim 12 \%$，高密度气体分数减少$\sim 13 \%$，并且气体的$\sim 20 \%$以大于逃逸速度（$500$ km/s）的速度流出。我们的结论是，类星体宿主星系在$z \geq 6$吸积不可忽略的宇宙气体量，但活动星系核的反馈淬火其恒星的形成占主导地位的强大的外流喷射气体的宿主星系晕。

英文摘要：

We investigate quasar outflows at $z \geq 6$ by performing zoom-in cosmological hydrodynamical simulations. By employing the SPH code GADGET-3, we zoom in the $2 R_{200}$ region around a $2 \times 10^{12} M_{\odot}$ halo at $z = 6$, inside a $(500 ~ {\rm Mpc})^3$ comoving volume. We compare the results of our AGN runs with a control simulation in which only stellar/SN feedback is considered. Seeding $10^5 M_{\odot}$ BHs at the centers of $10^{9} M_{\odot}$ halos, we find the following results. BHs accrete gas at the Eddington rate over $z = 9 - 6$. At $z = 6$, our most-massive BH has grown to $M_{\rm BH} = 4 \times 10^9 M_{\odot}$. Fast ($v_{r} > 1000$ km/s), powerful ($\dot{M}_{\rm out} \sim 2000 M_{\odot}$/yr) outflows of shock-heated low-density gas form at $z \sim 7$, and propagate up to hundreds kpc. Star-formation is quenched over $z = 8 - 6$, and the total SFR (SFR surface density near the galaxy center) is reduced by a factor of $5$ ($1000$). We analyse the relative contribution of multiple physical process: (i) disrupting cosmic filamentary cold gas inflows, (ii) reducing central gas density, (iii) ejecting gas outside the galaxy; and find that AGN feedback has the following effects at $z = 6$. The inflowing gas mass fraction is reduced by $\sim 12 \%$, the high-density gas fraction is lowered by $\sim 13 \%$, and $\sim 20 \%$ of the gas outflows at a speed larger than the escape velocity ($500$ km/s). We conclude that quasar-host galaxies at $z \geq 6$ are accreting non-negligible amount of cosmic gas, nevertheless AGN feedback quenches their star formation dominantly by powerful outflows ejecting gas out of the host galaxy halo.

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