标题： 缓慢自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$z>4$的低光度AGN群体，它们位于紧凑、红色的宿主星系中（“小红点”，或LRDs），在X射线中大部分未被检测到。 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$z\sim6$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射线最弱的情况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（SMBH）中，其自转为零，并且从极点方向以角度$>30^\circ$观测。 X射线辐射计修正在观测的$2-10$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SED表现出$\alpha_{\rm ox}$值超出标准范围，X射线弱性随着光学-紫外线光度增加；它们在X射线中也异常陡峭和软（中位光子指数$\Gamma=3.1$，众数为$\Gamma=4.4$）。 SED在X射线中较强时，当靠近热（$>10^8$K）和高度相对论性喷流观测时，其光谱更硬，并有一个高能峰，而X射线较弱的SED则没有这一特征。 在距离超大质量黑洞极区$10^\circ$的范围内观测，其中束流增强了X射线辐射，具有$\sim1.5\%$的概率，与LRD的X射线检测率相匹配。 下一代观测设备如AXIS将在从任何观测角度$z\sim6$处探测到X射线较弱的LRD。 尽管许多LRD中的超大质量黑洞已经被估计以超爱丁顿率吸积，但我们的模型通过要求它们的质量仅被高估了一个因子来解释$50\%$的群体。 $\sim3$。 总之，我们认为LRD包含缓慢旋转的超大质量黑洞，以适度超爱丁顿率吸积，具有大的覆盖因子和由强风增强的宽发射线，为它们的X射线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 exhibit $\alpha_{\rm ox}$ values outside standard ranges, with X-ray weakness increasing with optical-UV luminosity; they are also 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.