arXiv 1808.014392018-08-04astro-ph.SRastro-ph.GA

星际介质中的弓形激波化学

Bow-shock chemistry in the interstellar medium

L. N. Tram, P. Lesaffre, S. Cabrit, P. T. Nhung

摘要：

恒星是坏邻居：它们经常扰乱周围的环境。它们有时在星际介质中以非常快的速度运动。它们经常经历剧烈的喷射事件，在它们的邻居（喷流，风，超新星）上留下印记。这些超音速气流在喷射出的物质（弓形激波）和恒星环境（终止激波）中都产生激波。本论文的总体目的是通过研究这些激波，将恒星的性质与ISM联系起来。我们用Paris-Durham平面激波程序模拟了它们，该程序结合了大量与磁化ISM相关的微观物理和化学过程。在第一部分中，我们用Paris-Durham模型计算的一维平面激波的统计分布来模拟三维磁化轴对称弓形激波。对于第一次，我们系统地研究的几何形状，年龄，和各种其他参数上的H2激发图和发射线轮廓的效果。然后，我们将表明，这个三维弓形激波模型前所未有地提高了对猎户座BN-KL和BHR 71的H2观测的解释，并显示了如何在Herbig-Haro天体HH 54上的光谱分辨H2线发射轮廓可以用来提取丰富的动力学信息。在第二部分中，我们模拟了一维稳定的恒星风从AGB星，它触发的终止冲击，包括相关的物理和化学成分的巴黎-达勒姆代码。第一次，我们研究了随时间变化的转换原子分子氢沿着风的轨迹的“热”和“冷”AGB星。我们认为，低丰度的HI推断从观测是由于氢锁定在其分子形式。然后，我们试图再现HI 21厘米线轮廓中的“热”AGB（称为Y CVn）和“冷”AGB（称为CW狮子座）。

英文摘要：

Stars are bad neighbors: they often disturb their surroundings. They sometimes travel very fast through the interstellar medium (ISM). They frequently undergo violent ejection events which leave an imprint on their neighborhood (jets, winds, supernovae). These supersonic flows generate shocks both in the ejected material (bow shock) and in the stellar environment (termination shock). The global purpose of this thesis is to link the properties of stars and the ISM by studying these shocks. We model them with the Paris-Durham planar shock code, which incorporates a wealth of micro-physics and chemical processes relevant to the magnetized ISM. In the first part, we model 3D magnetized axis-symmetric bow shock by a statistical distribution of 1D planar shocks computed with the Paris-Durham model. For the first time, we examine systematically the effect of the geometry, age, and various other parameters on the H2 excitation diagram and emission line profiles. Then, we will show that this 3D bow shock model unprecedentedly improves interpretations of the H2 observations inOrion BN-KL and BHR71, and show how spectral resolved H2 line emission profiles on the Herbig-Haro objects HH54 can be used to extract a wealth of dynamical information. In the second part, we model 1D steady stellar winds from AGB stars, which trigger the termination shock, by including relevant physical and chemical ingredients in the Paris-Durham code. For the first time, we examine the time-dependent conversion of atomic to molecular hydrogen along the wind trajectories of "hot" and "cold" AGB stars. We suggest that the low abundance of HI inferred from observations is due to hydrogen locked in its molecular form. Then, we try to reproduce HI 21-cm line profile in a "hot" AGB (called Y CVn) and a "cold" AGB (called CW Leo).

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摘要：

英文摘要：

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