Observational Study of the Role of Magnetic Fields in Star Formation

了解恒星形成和磁场在星际云形成和演化中的作用的理论努力是广泛的，并且正在加速。然而，尽管近年来取得了重大进展，关于恒星形成的基本物理学仍然存在一些根本的未解之谜。如果密集分子云的寿命明显长于它们的自由落体坍缩时间，那么它们必须受到重力坍缩的支持。一种观点认为磁场提供了这种支持。这一假设可以通过测量稠密云的质量与磁通量之比来验证。另一个极端是，磁场很弱，分子云是间歇性现象，云的长时间支撑问题是无关紧要的。这个项目将直接或间接地测量一个大的、有统计学意义的分子云样本中的磁场强度，以帮助回答上述问题。由于必需的测量是对分子云的弱极化连续体和谱线发射的测量，星际磁场的测量仍然是最困难的天文观测之一，而且关于磁场的信息仍然非常稀少。星际磁场的测量不断取得进展，这对我们理解恒星形成的基本物理过程至关重要

AST-0205810PI CrutcherThe theoretical effort to understand star formation and the role of magnetic fields in the formation and evolution of interstellar clouds is extensive and accelerating. However, in spite of significant progress in recent years, there remain fundamental unanswered questions about the basic physics of star formation. If dense molecular clouds have lifetimes significantly longer than their free-fall collapse times, they must be supported against gravitational collapse. One view is that magnetic fields provide this support. This hypothesis can be tested by measurement of the mass to magnetic flux ratio in dense clouds. The other extreme is that magnetic fields are weak and that molecular clouds are intermittent phenomena, and that the problem of cloud support for long time periods is irrelevant. This project will measure, directly or indirectly, magnetic field strengths in a large, statistically meaningful sample of molecular clouds in order to help answer the above questions. Because the requisite measurements are of weakly polarized continuum and spectral-line emission from molecular clouds, measurements of interstellar magnetic fields remain among the most difficult of astronomical observations, and information about magnetic fields remains very sparse. It is crucial to our understanding of the fundamental physical process of star formation that measurements of interstellar magnetic fields continue to progress.***