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arXiv 2205.03215astro-ph.GAastro-ph.IM
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密度指数分析:恒星形成区密度剖面的引力驱动陡化

Density Exponent Analysis: Gravity-driven steepening of the density profiles of star-forming regions

Guang-Xing Li, Ji-Xuan Zhou

摘要:

星际分子云的演化是一个复杂的多尺度过程。幂律密度指数描述了密度分布的陡度,它已被用来表征云的密度结构,但它的使用通常仅限于球对称系统。在Level-Set方法的基础上,我们提出了一种新的形式,它可以在复杂密度分布的每个位置生成广义密度指数$k_ρ$的鲁棒映射。通过将其应用于高保真度,高动态范围的英仙座分子云的赫歇尔和普朗克卫星的数据构建的地图,我们发现,密度指数表现出令人惊讶的变化范围($-3.5 \lesssim k_ρ \lesssim -0.5$)。处于引力坍缩后期阶段的区域与较陡的密度剖面有关。在一个区域内,位于致密结构附近的气体具有非常陡峭的密度分布,其中$k_ρ \approx -3$是由于耗尽而形成的。这种密度指数分析揭示了不同的密度结构,形成了一个连贯的图片,引力坍缩导致的密度剖面的持续陡峭。我们希望我们的方法是有效的,在研究其他幂律密度结构,包括粒状材料和宇宙的大尺度结构。

英文摘要:

The evolution of molecular interstellar clouds is a complex, multi-scale process. The power-law density exponent describes the steepness of density profiles, and it has been used to characterize the density structures of the clouds yet its usage is usually limited to spherically symmetric systems. Importing the Level-Set Method, we develop a new formalism that generates robust maps of a generalized density exponent $k_ρ$ at every location for complex density distributions. By applying it to high fidelity, high dynamical range map of the Perseus molecular cloud constructed using data from the Herschel and Planck satellites, we find that the density exponent exhibits a surprisingly wide range of variation ($-3.5 \lesssim k_ρ \lesssim -0.5$). Regions at later stages of gravitational collapse are associated with steeper density profiles. Inside a region, gas located in the vicinities of dense structures has very steep density profiles with $k_ρ \approx -3$, which forms because of depletion. This density exponent analysis reveals diverse density structures, forming a coherent picture that gravitational collapse leads to a continued steepening of the density profile. We expect our method to be effective in studying other power-law-like density structures, including granular materials and the Large-Scale Structure of the Universe.

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