小红点：一个光度标签隐藏了大质量恒星形成和黑洞活动的多种光谱风味
Little Red Dots: One Photometric Tag Concealing Diverse Spectroscopic Flavors of Massive Star Formation and Black Hole Activity
AI总结：
研究通过光谱分析揭示小红点的多样性，发现其包含大质量恒星形成和黑洞活动的多种光谱特征。
摘要：
我们汇总了JWST/NIRSpec棱镜和MIRI数据，针对249个小红点（LRDs）在2.3<z<9.3范围内，形成了一个具有代表性的光谱子集。我们得到了一个中位数堆叠光谱，覆盖静止框架0.09-1.2μm，MIRI光度学将光谱能量分布延伸至4μm。四个额外的堆叠用于定义由光学到紫外光度比的子样本，显示LRDs是一个异质群体，跨越多样化的连续坡度和线特性。假设LRDs拥有超大质量黑洞（BHs）周围密集的气体云，并且恒星伴随这一核心，我们推断出BH质量约为10^6.0-6.5 M_⊙和恒星质量约为10^8.3 M_⊙，对应于BH与恒星质量比为1-2%。这些堆叠显示了普遍存在紫外和可见光FeII发射，表明直接观察到宽线区和高（但次埃达ington）吸积（λ_Edd=0.6±0.2）。我们发现远紫外区域有显著的恒星贡献，达到最蓝系统中的约80%。可能的沃尔夫-雷特特征（HeIIλ4687，氮线）被识别出来，追踪了一个年轻（3-7 Myr）的紧凑恒星爆发事件。我们还检测到了强巴尔末断裂以及不寻常的巴尔末、巴赫、[OIII]以及可见光和近红外HeI线比值，以及一个约4550埃的吸收（可能与FeII有关），所有这些都与高密度气体中温暖温度（4000-7000 K）的辐射转移效应一致。我们发现LRDs的多样性受到黑洞活动短（<20 Myr）和强烈阶段之间光度比的调节，最极端阶段持续约3-7 Myr，以接近埃达ington极限的辐射为特征，并且由大质量恒星（甚至超大质量，M_SMS≈10^5 M_⊙）主导的核和紧凑恒星爆发，所有这些都嵌套在密度高但尘埃含量适度的气体中，产生多种光学深度。
英文摘要：
We compile JWST/NIRSpec prism and MIRI data for 249 Little Red Dots (LRDs) at 2.3<z<9.3, forming a representative spectroscopic subset of NIRCam-selected LRDs. We derive a median stacked spectrum covering rest-frame 0.09-1.2 $μ$m, with MIRI photometry extending the spectral energy distribution to 4 $μ$m. Four additional stacks for subsamples defined by optical-to-UV luminosity ratios show that LRDs form a heterogeneous population spanning diverse continuum slopes and line properties. Assuming LRDs host super-massive black holes (BHs) surrounded by dense gas clouds, and stars accompany this core, we infer masses of $M_{BH}\sim10^{6.0-6.5}$ M$_\odot$ and $M_\bigstar\sim10^{8.3}$ M$_\odot$, corresponding to BH-to-stellar mass ratios of 1-2%. The stacks show ubiquitous UV and optical FeII emission, indicating a direct view of the broad-line region and high (but sub-Eddington) accretion ($λ_{Edd}=0.6\pm0.2$). We find a significant stellar contribution in the far-UV, reaching $\sim80$% in the bluest systems. Possible Wolf-Rayet features (HeII$λ$4687, nitrogen lines) are identified, tracing a young (3-7 Myr) compact starburst event. We also detect strong Balmer breaks and atypical Balmer, Paschen, [OIII], and optical and near-infrared HeI line ratios, and an absorption at $\sim4550$ Angstrom (probably linked to FeII), all consistent with radiative-transfer effects in high-density gas with warm temperatures (4000-7000 K). We find a diversity of LRD flavors modulated by the luminosity ratio between between a short ($\lesssim20$ Myr) and intense phase of BH activity, the most extreme stage lasting $\sim3-7$ Myr, characterized by near-Eddington-limit radiation, and a nuclear and compact starburst dominated by massive stars (even super-massive, $\mathrm{M}_\mathrm{SMS}\sim10^{5}$ M$_\odot$), all embedded in dense gas with modest dust content producing a variety of optical depths.
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