发表机构
Scuola Normale Superiore; Cosmic Frontier Center, University of Texas at Austin; INAF - Osservatorio Astronomico di Roma; Dipartimento di Fisica dell’Università di Trieste, Sez. di Astronomia; INAF - Osservatorio Astronomico di Trieste; INFN - Istituto Nazionale di Fisica Nucleare; INAF OAS -Osservatorio di astrofisica e scienza dello spazio（比萨高等师范学院; 德克萨斯大学奥斯汀分校宇宙前沿中心; 罗马天文台（意大利国家天体物理研究所）; 的里雅斯特大学物理系天文学部; 的里雅斯特天文台（意大利国家天体物理研究所）; 意大利国家核物理研究所; 空间天体物理学与科学观测站（意大利国家天体物理研究所））
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过宇宙学模拟和尘埃辐射转移，发现JWST小红点的V形连续谱等特征可在大型AGN宿主星系中自然涌现，无需将其视为独特天体类别。
AI 中文摘要
JWST发现了致密的高红移（z>=4）源，被称为小红点（LRDs），其特征是独特的V形连续谱。由于宽线AGN特征与非AGN连续谱共存，且伴有微弱的X射线和中红外辐射，它们的性质仍存在争议。我们研究了在大型AGN宿主星系的模拟中，LRDs的哪些性质自然涌现，哪些需要额外的物理过程。我们对同一大质量暗物质晕的两个宇宙学zoom-in模拟进行了后处理，其中一个包含黑洞增长和AGN反馈（AGNfid），另一个仅包含恒星形成和恒星反馈（SFonly）。我们分析了跨越z=6-9的快照，以探测不同的演化阶段。利用SKIRTv8，我们开发了一个前向建模框架，探索各种尘埃模型、尘埃与金属比率以及内在AGN光谱。我们生成模拟光谱和图像，以应用JWST观测LRD选择标准。尽管并非为模拟LRDs而设计，我们的AGNfid模拟自然重现了它们的性质：V形连续谱、具有静止系紫外复杂性的致密形态、紫外光度、消光、超大质量黑洞、亚爱丁顿吸积，以及大多数LRD典型的巴耳末跃变强度（约1-2）。光谱分解揭示，静止系紫外连续谱由恒星发射主导，而光学连续谱则源于尘埃衰减的AGN。尘埃几何结构以及AGN与恒星贡献之比驱动了LRDs和小蓝点（Little Blue Dots）之间的测光差异。我们的结果表明，LRDs不一定代表一类独特的天体。相反，它们的定义性性质可以在大型AGN宿主星系中，由恒星发射、被遮蔽的中心引擎和尘埃几何结构之间的相互作用而产生。超爱丁顿吸积、无尘气体柱、演化恒星种群以及光电离建模，需要用来检验这一框架是否能重现观测到的LRDs的多样性。
英文摘要
JWST has uncovered compact high-redshift (z>=4) sources, dubbed Little Red Dots (LRDs), characterised by a distinct V-shaped continuum. Their nature remains debated since broad-line AGN signatures coexist with non-AGN continua, marked by weak X-ray and mid-IR emission. We investigate which properties of LRDs naturally emerge within simulations of massive AGN host galaxies and which require additional physics. We post-process two cosmological zoom-in simulations of the same massive halo, one including black hole growth and AGN feedback (AGNfid) and the other with only star formation and stellar feedback (SFonly). We analyse snapshots spanning z=6-9 to probe different evolutionary stages. Using SKIRTv8, we develop a forward-modelling framework exploring various dust models, dust-to-metal ratios, and intrinsic AGN spectra. We generate mock spectra and images to apply JWST observational LRD selection criteria. Not designed to model LRDs, our AGNfid simulations naturally reproduce their properties: V-shaped continua, compact morphologies with rest-UV complexity, UV luminosities, attenuations, overmassive BHs, sub-Eddington accretion, and Balmer break strengths (~1-2) typical of most LRDs. Spectral decomposition reveals that the rest-UV continuum is dominated by stellar emission, whereas the optical continuum stems from a dust-attenuated AGN. Dust geometry and AGN-to-stellar contribution drive photometric differences between LRDs and Little Blue Dots. Our results suggest that LRDs do not necessarily represent a distinct class of objects. Instead, their defining properties can arise in massive AGN host galaxies from the interplay between stellar emission, an obscured central engine, and dust geometry. Super-Eddington accretion, dust-free gas columns, evolved stellar populations, and photoionisation modelling are required to test whether this framework reproduces the diversity of observed LRDs.
Comments24 pages, 14 figures (11 main text, 3 appendix). Submitted to Astronomy & Astrophysics (A&A)
