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arXiv 1607.03535astro-ph.GA
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银河系中心云的温度结构：通过turbulence气体加热的直接证据

Temperature structures in Galactic Center clouds - Direct evidence for gas heating via turbulence

K. Immer, J. Kauffmann, T. Pillai, A. Ginsburg, K. M. Menten

备注：
11 pages + 43 pages appendix, 4 tables, 35 figures, accepted for publication in A&A
发表信息：
A&A 595, A94 (2016)
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摘要：

位于银河系中心的中央分子带（CMZ）是研究极端条件下恒星形成过程的最佳模板，类似于高红移星系。我们观察到的飞行地图的para-H $_{2}$ CO过渡在218 GHz和291 GHz的7个银河系中心云。从H $_{2}$ CO（3 $_{2,1}-$ 2 $_{2,0}$）/H $_{2}$ CO（3 $_{0,3}-$ 2 $_{0,2}$）和H $_{2}$ CO（4 $_{2,2}-$ 3 $_{2,1}$）/H $_{2}$ CO（4 $_{0,4}-$ 3 $_{0,3}$）的温度敏感积分强度线比率结合辐射传输模型，我们产生我们的目标的气体温度图。这些跃迁对密度为$\sim$ 10 $^{5}$ cm $^{-3}$和温度<150 K的气体敏感。在我们的源中测得的气体温度都高于（>40 K）比他们的尘埃温度（$\sim$ 25 K）。我们的目标有一个复杂的速度结构，需要仔细解开不同的组件。我们为每个速度分量生成温度图，并显示各分量的温度不同，揭示了云中的温度梯度。结合温度测量和H $_{2}$ CO（4 $_{0,4}-$ 3 $_{0,3}$）/H $_{2}$ CO（3 $_{0,3}-$ 2 $_{0,2}$）的积分强度线比，我们将这种暖气体的密度限制为10 $^{4}-$ 10 $^{6}$ cm $^{-3}$。我们发现一个正相关的线宽的主要H $_{2}$ CO线与气体的温度，直接证据气体加热通过湍流。我们的数据是一致的湍流加热模型，密度n = 10 $^5$ cm $^{-3}$。

英文摘要：

The Central Molecular Zone (CMZ) at the center of our Galaxy is the best template to study star formation processes under extreme conditions, similar to those in high-redshift galaxies. We observed on-the-fly maps of para-H$_{2}$CO transitions at 218 GHz and 291 GHz towards seven Galactic Center clouds. From the temperature-sensitive integrated intensity line ratios of H$_{2}$CO(3$_{2,1}-$2$_{2,0}$)/H$_{2}$CO(3$_{0,3}-$2$_{0,2}$) and H$_{2}$CO(4$_{2,2}-$3$_{2,1}$)/H$_{2}$CO(4$_{0,4}-$3$_{0,3}$) in combination with radiative transfer models, we produce gas temperature maps of our targets. These transitions are sensitive to gas with densities of $\sim$10$^{5}$ cm$^{-3}$ and temperatures <150 K. The measured gas temperatures in our sources are all higher (>40 K) than their dust temperatures ($\sim$25 K). Our targets have a complex velocity structure that requires a careful disentanglement of the different components. We produce temperature maps for each of the velocity components and show that the temperatures of the components differ, revealing temperature gradients in the clouds. Combining the temperature measurements with the integrated intensity line ratio of H$_{2}$CO(4$_{0,4}-$3$_{0,3}$)/H$_{2}$CO(3$_{0,3}-$2$_{0,2}$), we constrain the density of this warm gas to 10$^{4}-$10$^{6}$ cm$^{-3}$. We find a positive correlation of the line width of the main H$_{2}$CO lines with the temperature of the gas, direct evidence for gas heating via turbulence. Our data is consistent with a turbulence heating model with a density of n = 10$^5$ cm$^{-3}$.

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