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arXiv 1204.3567astro-ph.GA
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超新星调节的ISM。I.多相结构

The supernova-regulated ISM. I. The multi-phase structure

F. A. Gent, A. Shukurov, A. Fletcher, G. R. Sarson, M. J. Mantere

摘要:

我们模拟了多相星际介质随机加热和搅拌的超新星,重力,微分旋转和其他参数的太阳邻域。在这里,我们详细描述了该模型的数值和物理方面,包括注入的热和动能的SN爆炸,辐射冷却,光电加热和各种运输过程。三维区域水平延伸1 kpc ^2,垂直延伸2 kpc,该模型通常涵盖气体数密度10^-5 ~ 10^2 cm^-3,温度10-10^8 K,局部速度高达10^3 km s^-1(马赫数高达25)。通过对气体数密度和温度的联合概率密度的检验,对模型化ISM的热结构进行了分类。我们证实,大部分的复杂性可以用三个阶段来描述,它们被大约10^3 K和5x10^5 K的温度边界所分隔。各相内气体密度的概率分布近似为对数正态分布。我们澄清相的分数体积和它的各种代理之间的连接,并推导出体积分数和填充因子定义的体积和概率平均值之间的确切关系。这些结果进行了讨论,在观测和计算的背景下。随机流的相关尺度是从速度自相关函数计算的,它是100 pc的顺序,并往往随着距离中平面的增长。我们使用两个不同的参数化的辐射冷却表明,气体的多相结构是强大的,因为它不依赖于这个选择显着。

英文摘要:

We simulate the multi-phase interstellar medium randomly heated and stirred by supernovae, with gravity, differential rotation and other parameters of the solar neighbourhood. Here we describe in detail both numerical and physical aspects of the model, including injection of thermal and kinetic energy by SN explosions, radiative cooling, photoelectric heating and various transport processes. With 3D domain extending 1 kpc^2 horizontally and 2 kpc vertically, the model routinely spans gas number densities 10^-5 - 10^2 cm^-3, temperatures 10-10^8 K, local velocities up to 10^3 km s^-1 (with Mach number up to 25). The thermal structure of the modelled ISM is classified by inspection of the joint probability density of the gas number density and temperature. We confirm that most of the complexity can be captured in terms of just three phases, separated by temperature borderlines at about 10^3 K and 5x10^5 K. The probability distribution of gas density within each phase is approximately lognormal. We clarify the connection between the fractional volume of a phase and its various proxies, and derive an exact relation between the fractional volume and the filling factors defined in terms of the volume and probabilistic averages. These results are discussed in both observational and computational contexts. The correlation scale of the random flows is calculated from the velocity autocorrelation function; it is of order 100 pc and tends to grow with distance from the mid-plane. We use two distinct parameterizations of radiative cooling to show that the multi-phase structure of the gas is robust, as it does not depend significantly on this choice.

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