The Role of Magnetic Fields in the Evolution of Molecular Clouds

理论研究提供了令人信服的论据，即磁场在星际介质中物质云形成恒星的过程中起着重要的，也许是必不可少的作用。对这些理论结果进行实证检验是非常重要的。可能的测试有：(1)通过观察中性原子氢、羟基和其他分子的谱线上的塞曼效应来测量和绘制稠密云中的磁场强度；(2)通过观测和绘制选定分子的毫米波线来确定云团、大小、运动学和密度，以评估磁场的动力学重要性；(3)测量云中分子种类的分数电离变化，以估计冻结磁场通量的条件；(4)云内质量磁通比及其变化的测定。这笔拨款支持伊利诺伊大学的Richard Crutcher博士与肯塔基大学的Thomas Troland博士合作开展的一项观察性研究项目，以测试上述所有领域的当前理论观点。

Theoretical research has provided compelling arguments that magnetic fields play an important and perhaps essential role in the formation of stars out of clouds of material in the interstellar medium. Empirical tests of these theoretical results are very important. Possible tests are: (1) the measurement and mapping of the strengths of the magnetic fields in dense clouds by observations of the Zeeman effect on spectral lines of neutral atomic hydrogen, hydroxyl, and other molecules; (2) determination of cloud masses, sizes, kinematics, and densities by observation and mapping of millimeter-wave lines of selected molecules in order to assess the dynamical importance of magnetic fields; (3) measurement of the variation of the fractional ionization of molecular species in clouds in order to estimate the conditions for freezing the magnetic field flux; and (4) determination of the mass-to-magnetic flux ratio and its variation within a cloud. This grant supports an observational research project conducted by Dr. Richard Crutcher, at the University of Illinois, in collaboration with Dr. Thomas Troland, at the University of Kentucky, to test the current theoretical ideas in all of the areas outlined above.