题 目：Bridging Local and Global Scales: Molecular Cloud and Star Formation in the Magellanic Clouds
报告人：Dr. Juergen Ott
（National Radio Astronomy Observatory, USA ）
摘 要：The Magellanic Clouds are the first milestone to understand molecular cloud and star formation on galaxy-wide scales. The Large Magellanic Cloud (LMC) exhibits an inclination that allows the detailed distribution of the giant molecular clouds (GMCs) while retaining the kinematic information (in contrast to the Galaxy). The Magellanic System is also close enough to identify all individual GMCs and thus provide enough objects to derive the statistical properties of their populations. We present CO observations with a resolution of 10pc of all GMCs in the LMC and deep observations of GMCs in the Small Magellanic Cloud (SMC). In addition, we will show interferometric observations of high density tracers (HCN, HCO+) towards a number of individual star forming regions at 2 pc resolution. We find that a simple column density argument is not sufficient for the transformation of atomic into molecular gas. It also appears that the radiation field that surrounds the molecular material only has little influence on most of the properties and thus the star formation abilities of individual GMCs. A trend, however, between the radiation field and the surface density of molecular material may exist. With the molecular gas being decoupled from the pressure equilibrium of their surroundings, the problem of star formation turns into a problem of molecular cloud formation. We will show how the GMC formation may depend on the global structure of a galaxy. Given the low metallicities of the Magellanic Clouds, our studies may have immediate impact in the understanding of 'normal' galaxies at high redshift. With their southern location, and their proximity that connects Galactic and extragalactic studies, the Magellanic System will be a prime target for future ALMA experiments.
时 间：2009年10月27日上午10:45
地 点：（北京西路2号）紫台大楼327教室
紫金山天文台学术委员会学术交流工作委员会
2009年10月15日
