Turbulence设定了恒星在高压环境中形成的初始条件
Turbulence sets the initial conditions for star formation in high-pressure environments
摘要：
尽管超音速湍流等温介质的理论模型很简单，但它们的预测成功地与太阳附近低压（P/k < 10^5 K cm^-3）分子云中观测到的气体结构和恒星形成活动相吻合。然而，这些理论是否适用于高压（P/k > 10^7 K cm^-3）环境中的云，比如银河系内部200 pc中央分子区（CMZ）和早期宇宙中的云，目前还不得而知。在这里，我们提出了ALMA 3毫米尘埃连续云，G0.253+0.016，这是沉浸在CMZ的高压环境中的排放。虽然它的柱密度PDF的对数正态形状和色散与太阳邻域云惊人地相似，但有一个重要的定量差异：它的平均柱密度高出1- 2个数量级。PDF中的相似性和差异与来自太阳邻域云的相似性和差异与CMZ高压环境下湍流云模型的预测相匹配。PDF显示在高柱密度下与对数正态的微小偏差，证实了G0.253+0.016的年轻性。它缺乏恒星的形成是一致的理论预测，环境依赖的体积密度阈值恒星形成的数量级高于太阳附近的云。我们的研究结果提供了第一个经验证据表明，目前的理论理解的分子云结构来自太阳附近也持有高压环境。因此，我们认为这些理论可能适用于理解早期宇宙中的恒星形成。
英文摘要：
Despite the simplicity of theoretical models of supersonically turbulent, isothermal media, their predictions successfully match the observed gas structure and star formation activity within low-pressure (P/k < 10^5 K cm^-3) molecular clouds in the solar neighbourhood. However, it is unknown if these theories extend to clouds in high-pressure (P/k > 10^7 K cm^-3) environments, like those in the Galaxy's inner 200 pc Central Molecular Zone (CMZ) and in the early Universe. Here we present ALMA 3mm dust continuum emission within a cloud, G0.253+0.016, which is immersed in the high-pressure environment of the CMZ. While the log-normal shape and dispersion of its column density PDF is strikingly similar to those of solar neighbourhood clouds, there is one important quantitative difference: its mean column density is 1--2 orders of magnitude higher. Both the similarity and difference in the PDF compared to those derived from solar neighbourhood clouds match predictions of turbulent cloud models given the high-pressure environment of the CMZ. The PDF shows a small deviation from log-normal at high column densities confirming the youth of G0.253+0.016. Its lack of star formation is consistent with the theoretically predicted, environmentally dependent volume density threshold for star formation which is orders of magnitude higher than that derived for solar neighbourhood clouds. Our results provide the first empirical evidence that the current theoretical understanding of molecular cloud structure derived from the solar neighbourhood also holds in high-pressure environments. We therefore suggest that these theories may be applicable to understand star formation in the early Universe.
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