Turbulence, coherence, and collapse: Three phases for core evolution
Turbulence, coherence, and collapse: Three phases for core evolution
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湍流、凝聚和崩溃：核心演化的三个阶段
DOI：
10.1093/mnras/stac2734
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发表时间：
2022
影响因子：
4.8
通讯作者：
Choudhury, Spandan
中科院分区：
文献类型：
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作者：
Offner, Stella S;Taylor, Josh;Markey, Carleen;Chen, Hope How-Huan;Pineda, Jaime E;Goodman, Alyssa A;Burkert, Andreas;Ginsburg, Adam;Choudhury, Spandan
我们研究的形成，演化和致密的核心，通过跟踪结构的磁流体动力学模拟的恒星形成云的崩溃。我们使用树状图算法识别核心，并利用机器学习技术，包括神经气体原型学习和模糊均值聚类分析核心的密度和速度分散分布以及六个散装属性。我们使用均匀流形近似和投影（UMAP）产生2-D可视化，这有助于物理特性和三个部分重叠的阶段之间的联系：i）未绑定的湍流结构（阶段I），ii）具有低湍流的相干核心（阶段II），iii）绑定核心，其中许多成为原恒星（阶段III）。在第二阶段，我们确定了人口的长寿命的相干核心，达到准平衡状态。大多数星前核形成于第二阶段，并在演化到第三阶段后成为原恒星。由于湍流云环境的影响，核的初始性质并不能唯一地预测最终的演化，即核的演化是随机的，核并不遵循单一的演化路径，相寿命分别为1.0 ± 0.1 × 105 yr、1.3 ± 0.2 × 105 yr和1.8 ± 0.3 × 105 yr。我们比较我们的结果NH3观测致密的核心。已知的相干核主要映射到第二阶段，而大多数湍流压力约束核映射到第一阶段或第三阶段。我们预测，观察到的无星核心的一个显着的分数有未解决的相干区域，观察到的无星核心的20%将不会形成恒星。除了通常的散装性能的核心径向剖面的测量将能够更准确地预测核心的演变。
We study the formation, evolution, and collapse of dense cores by tracking structures in a magnetohydrodynamic simulation of a star-forming cloud. We identify cores using the dendrogram algorithm and utilize machine learning techniques, including Neural Gas prototype learning and Fuzzyc-means clustering to analyse the density and velocity dispersion profiles of cores together with six bulk properties. We produce a 2-d visualization using a Uniform Manifold Approximation and Projection (UMAP), which facilitates the connection between physical properties and three partially-overlapping phases: i) unbound turbulent structures (Phase I), ii) coherent cores that have low turbulence (Phase II), and iii) bound cores, many of which become protostellar (Phase III). Within Phase II, we identify a population of long-lived coherent cores that reach a quasi-equilibrium state. Most prestellar cores form in Phase II and become protostellar after evolving into Phase III. Due to the turbulent cloud environment, the initial core properties do not uniquely predict the eventual evolution, i.e. core evolution is stochastic, and cores follow no one evolutionary path. The phase lifetimes are 1.0 ± 0.1 × 105yr, 1.3 ± 0.2 × 105yr, and 1.8 ± 0.3 × 105yr for Phase I, II, and III, respectively. We compare our results to NH3observations of dense cores. Known coherent cores predominantly map into Phase II, while most turbulent pressure-confined cores map to Phase I or III. We predict that a significant fraction of observed starless cores have unresolved coherent regions and that ≳20 per cent of observed starless cores will not form stars. Measurements of core radial profiles in addition to the usual bulk properties will enable more accurate predictions of core evolution.