发表机构
School of Earth and Space Exploration, Arizona State University; Steward Observatory, University of Arizona; Kavli Institute for Cosmology, University of Cambridge; Cavendish Laboratory, University of Cambridge; Department of Physics and Astronomy, University of California, Riverside（亚利桑那州立大学地球与空间探索学院; 亚利桑那大学斯图尔德天文台; 剑桥大学卡弗里宇宙学研究所; 剑桥大学卡文迪许实验室; 加州大学河滨分校物理与天文学系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究探讨爱丁顿极限超爱丁顿型小蓝点对氦电离的影响，发现多数小蓝点若为超爱丁顿态会与氦电离观测约束冲突，需小逃逸分数或低丰度，结论对黑洞极紫外光谱形状敏感。
AI 中文摘要
詹姆斯·韦布空间望远镜（JWST）在红移z≥4处发现了大量微弱的活动星系核（AGN），这些天体具有宽发射线、致密形态和蓝紫外-光学连续谱特征。这些被称为“小蓝点”（Little Blue Dots, LBDs）的天体被认为与更具争议的“小红点”（Little Red Dots, LRDs）属于同一类天体，两者的差异主要源于观测视角效应。在该情景中，爱丁顿极限超爱丁顿吸积过程产生了高极紫外（EUV）辐射和弱X射线发射，这一机制可解释两类天体的特性。我们研究了该超爱丁顿情景对氦电离时间的影响。我们发现，支持氦电离结束不早于z≈3的观测结果，不支持在观测到的3≤z≤7的LBDs中，多数处于高度超爱丁顿状态的情景。在我们的基准超爱丁顿吸积情景中，假设LBDs占M_mUV<-18的星系群体的5%，且平均逃逸分数为15%（与近期观测结果相当），则该状态下的LBD群体占比必须≤10%。我们的约束假设LBDs主导氦电离预算，若明亮类星体也有显著贡献，该约束会更严格。若多数LBDs处于超爱丁顿状态，它们需要具有小的逃逸分数（≤1.5%）和/或丰度低于观测结果。我们的结论对超爱丁顿黑洞的EUV光谱形状敏感，这有待进一步研究。
英文摘要
The James Webb Space Telescope (JWST) has identified an abundant population of faint Active Galactic Nuclei (AGN) at $z \gtrsim 4$ which display broad emission lines, compact morphologies, and blue ultraviolet--optical continua. These ``Little Blue Dots' (LBDs) have been suggested to belong to the same family of objects as the more controversial ``Little Red Dots' (LRDs), with differences between the two largely owing to viewing angle effects. In this scenario, super-Eddington accretion resulting in high Extreme UV (EUV) and weak X-ray emission is invoked to explain the properties of both populations. We study the consequences of this super-Eddington scenario for the timing of Helium reionization. We find that observations which support an end to helium reionization no earlier than $z \approx 3$ disfavor scenarios in which the majority of observed $3 \lesssim z \lesssim 7$ LBDs are highly super-Eddington. For our fiducial super-Eddington accretion scenario, we find that the fraction of the LBD population in this state must be $\lesssim 10\%$, assuming LBDs make up $5\%$ of the $M_{ m UV} < -18$ galaxy population and have average escape fractions of $15\%$, comparable to recent observations. Our constraint assumes that LBDs dominate the Helium reionization budget, and would be tighter if bright quasars also contributed significantly. For a majority of LBDs to be super-Eddington, they would need to have small escape fractions ($\lesssim 1.5\%$) and/or be less abundant than observations suggest. Our conclusions are sensitive to the shape of the EUV spectra of super-Eddington black holes, motivating further study.
Comments9+1 pages, 4+1 figures, submitted to ApJL. Comments welcome
