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Self-Organization in Star Formation and Internal Structure of Molecular Clouds

恒星形成的自组织和分子云的内部结构

基本信息

批准号：
09640318
负责人：
HANAWA Tomoyuki
金额：
$ 0.45万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640318/
关键词：
Star Formation Self-Gravity Self-Organization Numerical Simulation Rotation 連星

项目摘要

Molecular clouds, in which stars form activcly, contain hierarchical internal structures ; they contain elongated filamentary clouds involving spherical cloud cores in which binaries or triplcts are embedded. This hicrarchical structure is produced when stars are formed by gravitational collapse. In this project we regard the deformation of molecular cloud during its gravitational collapse as self-organization. To understand the physics of gravitational collapse, we performed numerical simulations.We followed the gravitational collapse of initially either a spherical, filamentnry, or disky cloud in our numerical simulations taking account of self-gravity, inaguctic fields, and rotation. Although we tried various initial models, the numerical rcsults are summarized by similarity solutions characterized by the sound speed of gas. The final product in a numerical simulation depends little on the initial mass, magnetic field, and angular momentum of the cloud. This indicates that the structure of a gravitationally contracting cloud is determined by the balance between the gravity and gas pressure.The major findings from numerical simulations and theoretical analysis are as follows.1.A magnetized cloud collapses to form a similar disk irrespectively of its initial magnetic field strength. The density and velocity of the disk is well approximated by a similarity solution having the sound speed as a parameter. 2. A gravitationally contracting disk often deforms into a bar. A gravitationally contracting sphere often deforms into a disk or bar. Since a bar is unstable against fragmentation, it is expected to produce a binary or triplet of stars. 3. A gravitationally collapsing filament is well approximated by a similarity solution.

分子云是恒星活跃形成的地方，内部结构有层次性;它们包含细长的对流云，云核呈球形，其中嵌入了双星或三颗星。这种星系结构是在恒星因引力坍缩而形成时产生的。在这个项目中，我们把分子云在引力坍缩过程中的变形看作是自组织。为了理解引力坍缩的物理过程，我们进行了数值模拟，在考虑自引力、无引力场和旋转的情况下，我们跟踪了最初的球形云、无引力云或盘状云的引力坍缩。虽然我们尝试了不同的初始模型，但数值结果都是由以气体声速为特征的相似解来概括的。数值模拟的最终结果几乎不依赖于云的初始质量、磁场和角动量。数值模拟和理论分析的主要结果如下：1.无论初始磁场强度如何，磁化云坍缩形成一个相似的圆盘。的密度和速度的磁盘是很好的近似的相似性解决方案具有声速作为参数。2.一个因引力而收缩的圆盘经常会变形成一个棒状。一个引力收缩的球体经常变形为圆盘或棒。由于棒是不稳定的对分裂，它预计将产生一个双星或三重星。3.引力坍缩的暗条可以用相似解很好地近似。