Chemical Modeling of Orion Nebula Cluster Disks: Evidence for Massive, Compact Gas Disks with Interstellar Gas-to-dust Ratios
Chemical Modeling of Orion Nebula Cluster Disks: Evidence for Massive, Compact Gas Disks with Interstellar Gas-to-dust Ratios
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DOI：
10.3847/1538-4357/acaf77
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发表时间：
2022-12
期刊：
影响因子：
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通讯作者：
R. D. Boyden;J. Eisner
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文献类型：
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作者：
R. D. Boyden;J. Eisner
星团环境预计将在星周盘的演化中发挥核心作用。我们使用热化学模型来约束猎户座星云团 (ONC) 中 20 个 II 级盘的尘埃和气体质量、盘尺寸、紫外线和 X 射线辐射场、观察几何形状以及中心恒星质量。我们将大型圆盘模型网格拟合到 350 GHz 连续谱、CO J = 3 − 2 和 HCO+ J = 4 − 3 阿塔卡马大型毫米/亚毫米阵列对每个目标的观测，并介绍了对在明亮分子云背景下吸收中检测到的气盘干涉观测进行建模的过程。我们发现ONC盘巨大而紧凑，典型半径<100 au，气体质量≥10−3 M ⊙，气尘比≥100。从我们的模型中得出的类星际介质气体与尘埃的比率表明，与附近低质量恒星形成区域常见的大质量和扩展气体盘相比，ONC中紧凑的外部辐射盘更不容易发生气相二氧化碳消耗。巨大气盘的存在表明外部光蒸发可能最近才开始在 ONC 中运行；尽管目前尚不清楚其他星团成员是否比我们样本中的成员更古老且更蒸发。最后，我们将动态推导的恒星质量与进化模型预测的恒星质量进行比较，发现非常一致。我们的研究显着增加了质量范围≤0.5 M 的动态质量测量数量，表明 ONC 是获得低质量 M 矮星动态质量测量大样本的理想区域。
The stellar cluster environment is expected to play a central role in the evolution of circumstellar disks. We use thermochemical modeling to constrain the dust and gas masses, disk sizes, UV and X-ray radiation fields, viewing geometries, and central stellar masses of 20 class II disks in the Orion Nebula Cluster (ONC). We fit a large grid of disk models to 350 GHz continuum, CO J = 3 − 2, and HCO+ J = 4 − 3 Atacama Large Millimeter/submillimeter Array observations of each target, and we introduce a procedure for modeling interferometric observations of gas disks detected in absorption against a bright molecular cloud background. We find that the ONC disks are massive and compact, with typical radii <100 au, gas masses ≥10−3 M ⊙, and gas-to-dust ratios ≥100. The interstellar‐medium‐like gas-to-dust ratios derived from our modeling suggest that compact, externally irradiated disks in the ONC are less prone to gas-phase CO depletion than the massive and extended gas disks that are commonly found in nearby low-mass star-forming regions. The presence of massive gas disks indicates that external photoevaporation may have only recently begun operating in the ONC; though it remains unclear whether other cluster members are older and more evaporated than the ones in our sample. Finally, we compare our dynamically derived stellar masses with the stellar masses predicted from evolutionary models and find excellent agreement. Our study has significantly increased the number of dynamical mass measurements in the mass range ≤0.5 M ⊙, demonstrating that the ONC is an ideal region for obtaining large samples of dynamical mass measurements toward low-mass M-dwarfs.