钙三重线吸收在小红点中普遍存在
Calcium Triplet Absorption is Common around Little Red Dots
- Princeton University（普林斯顿大学）
- Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）
- University of Hawai‘i（夏威夷大学）
- The Johns Hopkins University（约翰斯·霍普金斯大学）
- Swinburne University of Technology（斯威本科技大学）
- The University of Texas at Austin（德克萨斯大学奥斯汀分校）
- Tsinghua University（清华大学）
- The Pennsylvania State University（宾夕法尼亚州立大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过JWST/NIRSpec数据在17个小红点样本中探测到钙三重线吸收，证实其周围存在光学厚大气，为LRD的冷光球层模型提供新证据。
AI中文摘要：
我们提出了新的证据，表明小红点（LRDs）周围存在光学厚大气，其形式为静止系8500埃处的钙吸收，即钙三重线（CaT）。基于在一个本地LRD类似物（“蛋”，Lin等人2025年）中探测到CaT吸收，我们研究了17个LRD（$2 < z < 5$）的档案样本中静止系8500埃附近的区域，这些样本具有JWST/NIRSpec光栅数据。我们在三个独立源中探测到CaT吸收，并发现平均吸收等值宽度（EW）EW$_{\rm CaT} \approx -5$ 埃。在这三个探测中，有两个接近恒星集成光中所见的最大吸收深度。鉴于CaT附近的连续谱可能由中央引擎主导，我们认为吸收体很可能与LRD相关。这种吸收在历史上并未与AGN中央引擎的任何组成部分相关联，但为LRD提出的冷、光学厚光球层自然会产生这种吸收。我们观测到的EW$_{\rm CaT}$可以通过相对低金属丰度（[M/H]$<-1$）的静水压大气模型结合有效温度$T_{\rm eff} > 4500$ K来匹配。或者，该分布可以在低光球气体密度$\rho_{\rm ph}<10^{-11}{\rm~g~cm^{-3}}$下匹配，这需要基于动力学理由的非静水压气体结构。未来，金属吸收线应成为探测LRD气体条件乃至可能封闭质量的强大补充探针。
英文摘要：
We present new evidence for an optically thick atmosphere surrounding Little Red Dots (LRDs) in the form of Ca absorption at rest-frame 8500A, the calcium triplet (CaT). Building on the detection of CaT absorption in one local LRD analog (the "Egg", Lin et. al. 2025), we investigate the region around rest-frame 8500A for an archival sample of 17 LRDs ($2 < z < 5$) with JWST/NIRSpec grating data. We detect CaT absorption in three individual sources, and find that on average there is an absorption equivalent width (EW) EW$_{\rm CaT} \approx -5$ A. Among the three detections, two are approaching the deepest absorption seen in integrated light from stars. Given that the continuum around CaT is probably dominated by the central engine, we argue that the absorbers are likely to be associated with the LRD. Such absorption has not historically been associated with any components of an AGN central engine, but a cool, optically thick photosphere as proposed for LRDs would naturally produce such absorption. The EW$_{\rm CaT}$ that we observe can be matched by hydrostatic atmosphere models at relatively low metallicity ([M/H]$<-1$) combined with an effective temperature $T_{\rm eff} > 4500$ K. Alternatively, the distribution can be matched at a low photospheric gas density $ρ_{\rm ph}<10^{-11}{\rm~g~cm^{-3}}$ that requires a non-hydrostatic gas structure on dynamical grounds. In the future, metal absorption lines should be a powerful complementary probe of the gas conditions, and possibly the enclosed mass, of LRDs.
