报告题目：Molecular Cloud Fragmentation Channeled by Magnetic Fields

　　报 告 人：Prof. Huabai Li (The Chinese University of Hong Kong)

　　摘    要：Star formation is still a mystery. Gravity alone is not able to explain the low star-formation efficiency (~10%) in molecular clouds. While the main-stream models agree on that turbulence can help to support a cloud against self-gravity, the role played by magnetic fields is very controversial. The recent multi-scale observation of cloud magnetic fields in NGC 6334 sheds light on the debate. The field direction does not change significantly from 100 to 0.01 pc, implying that the field is dynamically important compared to gravity and turbulence. In turn, the cloud fragmentation is channeled by the field and self-similar: at multi-scales, elongated cloud structures tend to be perpendicular to the field, which is symmetrically pinched at the ends of cloud elongations. Moreover, the field strength is proportional to the 0.4-power of the density, which is an evidence that the gravitational contraction is channeled by the magnetic field.

　　时    间：2015年06月02日（星期二）10：30

　　地    点：（北京西路2号）紫台大楼619教室

　　联 系 人：赵奥（83332112）

欢迎大家积极参加！

　　                                                   紫金山天文台学术委员会