On the Three-dimensional Structure of Local Molecular Clouds
On the Three-dimensional Structure of Local Molecular Clouds
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DOI：
10.3847/1538-4357/ac1f96
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发表时间：
2021-09
期刊：
影响因子：
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通讯作者：
C. Zucker;A. Goodman;J. Alves;S. Bialy;E. Koch;J. Speagle;M. Foley;D. Finkbeiner;R. Leike
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文献类型：
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作者：
C. Zucker;A. Goodman;J. Alves;S. Bialy;E. Koch;J. Speagle;M. Foley;D. Finkbeiner;R. Leike
我们利用 Leike 等人的 1 pc 空间分辨率。三维 (3D) 尘埃图来表征附近分子云的 3D 结构 (d ≲ 400 pc)。我们首先在 3D 体积密度空间中“骨架化”云，以确定它们的“脊柱”，我们将其投影到天空上，以约 1% 的不确定性限制云距离。对于每个云，我们确定其 3D 脊柱周围的平均径向体积密度分布，并使用高斯和 Plummer 函数拟合该分布。径向体积密度分布可以通过二分量高斯函数很好地描述，这与具有宽阔、低密度外层和狭窄、高密度内层的云一致。外封套与内封套宽度之比约为 3:1。我们假设这两种成分可能正在追踪原子和扩散分子气体之间或不稳定和冷中性介质之间的转变。类普拉默模型也可以提供良好的拟合，分子云表现出密度为 n 的浅幂律翼，在大半径处像 n −2 一样脱落。使用贝叶斯模型选择，我们发现使用单个高斯参数化云的剖面是不受欢迎的。我们将我们的结果与二维尘埃消光图进行比较，发现 3D 尘埃通过集成方法保真度地恢复了总云质量，仅在较高消光水平（A V ≳ 2-3 mag）时出现偏差。这里描述的 3D 云结构将能够与模拟中生成的合成云进行比较，从而为星际介质中分子云的起源和命运提供前所未有的见解。
We leverage the 1 pc spatial resolution of the Leike et al. three-dimensional (3D) dust map to characterize the 3D structure of nearby molecular clouds (d ≲ 400 pc). We start by “skeletonizing” the clouds in 3D volume density space to determine their “spines,” which we project on the sky to constrain cloud distances with ≈1% uncertainty. For each cloud, we determine an average radial volume density profile around its 3D spine and fit the profiles using Gaussian and Plummer functions. The radial volume density profiles are well described by a two-component Gaussian function, consistent with clouds having broad, lower-density outer envelopes and narrow, higher-density inner layers. The ratio of the outer to inner envelope widths is ≈3:1. We hypothesize that these two components may be tracing a transition between atomic and diffuse molecular gas or between the unstable and cold neutral medium. Plummer-like models can also provide a good fit, with molecular clouds exhibiting shallow power-law wings with density, n, falling off like n −2 at large radii. Using Bayesian model selection, we find that parameterizing the clouds’ profiles using a single Gaussian is disfavored. We compare our results with two-dimensional dust extinction maps, finding that the 3D dust recovers the total cloud mass from integrated approaches with fidelity, deviating only at higher levels of extinction (A V ≳ 2–3 mag). The 3D cloud structure described here will enable comparisons with synthetic clouds generated in simulations, offering unprecedented insight into the origins and fates of molecular clouds in the interstellar medium.