JWST has revealed a ubiquitous population of “little red dots” (LRDs) at z ≳ 4, selected via their red rest-frame optical emission and compact morphologies. They are thought to be reddened by dust, whether in tori of active galactic nuclei (AGNs) or the interstellar medium, though none have direct dust detections to date. Informed by the average characteristics of 675 LRDs drawn from the literature, we provide ballpark constraints on the dust characteristics of the LRD population and estimate they have average dust masses of 〈Mdust〉=(1.6−0.9+4.8)×104 M _⊙, luminosities of 〈LIR〉=(8−5+3)×1010 L _⊙, and temperatures of 〈Tdust〉=110−36+21 K. Notably, the spectral energy distributions are thought to peak at ∼100 K (rest-frame 20–30 μm) regardless of heating mechanism, whether AGN or star formation. LRDs’ compact sizes R _eff ∼ 100 pc are the dominant factor contributing to their low estimated dust masses. Our predictions likely mean LRDs have, on average, a submillimeter emission factor of ∼100× fainter than current Atacama Large Millimeter/submillimeter Array limits provide. The star-to-dust ratio is a factor ∼100× larger than expected from dust formation models if one assumes the rest-optical light is dominated by stars; this suggests stars do not dominate. Despite their high apparent volume density, LRDs contribute negligibly (0.1%) to the cosmic dust budget at z ≳ 4 due to their low dust masses.

中文翻译：

---

小红点中的灰尘


JWST 揭示了在 z ≳ 4 处无处不在的“小红点”（LRD） 群体，这些点是通过它们的红色静止框架光学发射和紧凑的形态选择的。它们被认为被尘埃变红，无论是在活跃的星系核 （AGN） 的 tori 还是在星际介质中，尽管迄今为止还没有直接的尘埃探测到。根据文献中 675 个 LRD 的平均特征，我们对 LRD 种群的尘埃特性提供了大致的约束，并估计它们的平均尘质量〈Mdust〉=（1.6-0.9+4.8）×104 M_⊙，〈LIR〉的光度=（8-5+3）×1010 L_⊙，温度〈Tdust〉=110-36+21 K。值得注意的是，无论加热机制如何，光谱能量分布被认为在 ∼100 K（静止框架 20-30 μm）达到峰值， 无论是 AGN 还是恒星形成。LRD 的紧凑尺寸 R_eff ∼ 100 pc 是导致其估计粉尘质量低的主要因素。我们的预测可能意味着 LRD 的平均亚毫米发射系数比当前阿塔卡马大型毫米/亚毫米阵列限制提供的亚毫米发射系数低约 100× 微弱。如果假设其余光学光以恒星为主，那么星尘比尘埃形成模型的预期要大 ∼100×这表明恒星并不占主导地位。尽管 LRD 的表观体积密度很高，但由于它们的尘埃质量低，它们在 z ≳ 0.1 处对宇宙尘埃预算的贡献可以忽略不计 （4%）。