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arXiv 2102.06459astro-ph.GA
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L1688中从相干核到周围云的过渡

Transition from Coherent Cores to Surrounding Cloud in L1688

Spandan Choudhury, Jaime E. Pineda, Paola Caselli, Stella S. R. Offner, Erik Rosolowsky, Rachel K. Friesen, Elena Redaelli, Ana Chacón-Tanarro, Yancy Shirley, A… 展开作者

Spandan Choudhury, Jaime E. Pineda, Paola Caselli, Stella S. R. Offner, Erik Rosolowsky, Rachel K. Friesen, Elena Redaelli, Ana Chacón-Tanarro, Yancy Shirley, Anna Punanova, Helen Kirk

备注：
37 pages, 33 figures, 1 table. Accepted for publication in A&A
发表信息：
A&A 648, A114 (2021)
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摘要：

恒星形成于冷而致密的核心，表现出亚音速的速度分散。母体分子云显示出较高的温度和超音速弥散。从核心到云的转变已经在速度分散中观察到，但温度和丰度的变化是未知的。我们的目标是研究过渡从核心到环境云的温度和速度的分散使用一个单一的示踪剂。我们使用来自Green Bank Ammonia Survey的L1688中的NH3（1，1）和（2，2）图，平滑到1 '，并从拟合中确定物理性质。我们确定的相干核心和研究的温度和速度的变化，从核心到周围的云分散。我们得到了一个动力学温度图跟踪扩展云，改进以前的地图跟踪主要是核心。云是4-6 K比核心温暖，并显示出较大的速度色散（差异。= 0.15-0.25 km/s）。与基于Herschel的测量相比，我们发现核心显示动力学温度$\approx$ 1.8 K低于尘埃温度，而气体温度高于尘埃温度在云中。我们发现一个平均p-NH3分数丰度（相对于H2）的$(4.2\pm0.2) \times 10^{-9}$对连贯的核心，和$(1.4\pm0.1) \times 10^{-9}$以外的核心边界。使用堆叠的光谱，我们检测到两个组件，一个窄，一个宽，对核心和他们的邻居。我们发现在窄的组件中的湍流与结构的大小相关（Pearson-r=0.54）。与这些未解决的区域测量，我们得到了$σ_{v,NT}\propto r^{0.5}$，类似于以前的研究结果，使用多种示踪剂的双折射大小的关系。我们发现，亚音速分量延伸到0.15 pc超出典型的相干边界，揭示了更大范围的相干核心，并显示出逐渐过渡到相干超过0.2 pc。

英文摘要：

Stars form in cold dense cores showing subsonic velocity dispersions. The parental molecular clouds display higher temperatures and supersonic velocity dispersions. The transition from core to cloud has been observed in velocity dispersion, but temperature and abundance variations are unknown. We aim to study the transition from cores to ambient cloud in temperature and velocity dispersion using a single tracer. We use NH3 (1,1) and (2,2) maps in L1688 from the Green Bank Ammonia Survey, smoothed to 1', and determine the physical properties from fits. We identify the coherent cores and study the changes in temperature and velocity dispersion from cores to the surrounding cloud. We obtain a kinetic temperature map tracing the extended cloud, improving from previous maps tracing mostly the cores. The cloud is 4-6 K warmer than the cores, and shows a larger velocity dispersion (diff. = 0.15-0.25 km/s). Comparing to Herschel-based measurements, we find that cores show kinetic temperature $\approx$1.8 K lower than the dust temperature; while the gas temperature is higher than the dust temperature in the cloud. We find an average p-NH3 fractional abundance (with respect to H2) of $(4.2\pm0.2) \times 10^{-9}$ towards the coherent cores, and $(1.4\pm0.1) \times 10^{-9}$ outside the core boundaries. Using stacked spectra, we detect two components, one narrow and one broad, towards cores and their neighbourhoods. We find the turbulence in the narrow component to be correlated to the size of the structure (Pearson-r=0.54). With these unresolved regional measurements, we obtain a turbulence-size relation of $σ_{v,NT}\propto r^{0.5}$, similar to previous findings using multiple tracers. We discover that the subsonic component extends up to 0.15 pc beyond the typical coherent boundaries, unveiling larger extents of the coherent cores and showing gradual transition to coherence over ~0.2 pc.

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