标题： 缓慢旋转黑洞的弱超爱丁顿吸积解释了小红点的X射线弱性 显示英文标题

标题： Mildly Super-Eddington Accretion Onto Slowly-Spinning Black Holes Explains the X-Ray Weakness of the Little Red Dots

摘要： JWST揭示了一个在$z>4$处的低光度AGN群体，在紧凑、红色的宿主中（称为“小红点”或LRDs），这些在X射线中大多未被检测到。 我们使用GRRMHD模拟研究了这一现象，模拟的是超爱丁顿吸积到质量为$M_\bullet=10^7 \,\rm M_\odot$的超大质量黑洞（SMBH）在$z\sim6$处的情况，代表了中位群体；我们得到的光谱能量分布（SEDs）本质上是X射线弱的。 X射线最弱的水平出现在以轻微超爱丁顿率（$1.4<f_{\rm Edd}<4$）吸积的超大质量黑洞中，自转为零，并且从极点方向以$>30^\circ$的角度观测。 X射线光度计修正在观测的$2-10$keV 波段达到$\sim10^4$在$z=6$，比X射线堆叠的最高限制高$\sim5$倍。 大多数光谱能量分布在X射线中极其陡峭和软（中位数光子指数$\Gamma=3.1$，众数为$\Gamma=4.4$）。 在X射线中强烈的光谱能量分布在接近热（$>10^8$K）和高度相对论性喷流时具有更硬的光谱和高能峰，而X射线弱的光谱能量分布缺乏这一特征。 在距离 SMBH 极点$10^\circ$的位置观察到它，其中束流增强了 X 射线辐射，这种概率为$\sim1.5\%$，与 LRD 的 X 射线探测率相符。 下一代观测设备如 AXIS 将能够从任何观测角度检测到 X 射线较弱的 LRDs，其红移为$z\sim6$。 尽管许多 LRD 中的 SMBH 已经估计以超爱丁顿吸积率吸积，但我们的模型通过要求它们的质量仅被高估了一个因子$\sim3$来解释其种群中的$50\%$。 总之，我们认为 LRDs 中包含缓慢旋转的 SMBH，它们以适度超爱丁顿的吸积率吸积，具有大的覆盖因子和由强风增强的宽发射线，为其 X 射线的微弱性提供了一个自洽的解释，并补充了其他模型。 显示英文摘要

摘要： JWST has revealed a population of low-luminosity AGN at $z>4$ in compact, red hosts (the "Little Red Dots", or LRDs), which are largely undetected in X-rays. We investigate this phenomenon using GRRMHD simulations of super-Eddington accretion onto a SMBH with $M_\bullet=10^7 \,\rm M_\odot$ at $z\sim6$, representing the median population; the SEDs that we obtain are intrinsically X-ray weak. The highest levels of X-ray weakness occur in SMBHs accreting at mildly super-Eddington rates ($1.4<f_{\rm Edd}<4$) with zero spin, viewed at angles $>30^\circ$ from the pole. X-ray bolometric corrections in the observed $2-10$ keV band reach $\sim10^4$ at $z=6$, $\sim5$ times higher than the highest constraint from X-ray stacking. Most SEDs are extraordinarily steep and soft in the X-rays (median photon index $\Gamma=3.1$, mode of $\Gamma=4.4$). SEDs strong in the X-rays have harder spectra with a high-energy bump when viewed near the hot ($>10^8$ K) and highly-relativistic jet, whereas X-ray weak SEDs lack this feature. Viewing a SMBH within $10^\circ$ of its pole, where beaming enhances the X-ray emission, has a $\sim1.5\%$ probability, matching the LRD X-ray detection rate. Next-generation observatories like AXIS will detect X-ray weak LRDs at $z\sim6$ from any viewing angle. Although many SMBHs in the LRDs are already estimated to accrete at super-Eddington rates, our model explains $50\%$ of their population by requiring that their masses are overestimated by a mere factor of $\sim3$. In summary, we suggest that LRDs host slowly spinning SMBHs accreting at mildly super-Eddington rates, with large covering factors and broad emission lines enhanced by strong winds, providing a self-consistent explanation for their X-ray weakness and complementing other models.