An Observational Study of Expanding Gas Shell in the Galaxy and the Magellanic Clouds

这项研究旨在揭示星系演化中恒星形成的物理过程，重点是超级壳层可能发挥的作用。我们采用的方法是详细研究本地群、银河系和大小麦哲伦云三个星系中的分子云和恒星形成。我们揭示了银河系尺度上分子云演化模式的前所未有的细节，并得出结论：与包括随机湍流压缩在内的其他过程相比，超壳层的作用并不占优势。在这项研究过程中，我们首先证明了大麦哲伦星云是三个星系中最可靠的，因为另外两个星系由于污染或恒星形成不太活跃，具有重要意义的样本数要少得多，只有20-30个。另一方面，大麦哲伦星云有近200个样本，可以与大质量恒星形成的迹象进行重大比较。我们使用其他地方的HII区和年轻星团的观测数据来确定单个分子云中的大质量恒星的形成，以揭示三类分子云：(1)无星，(2)只有HII区，(3)有星团和丰富的HII区。这三个类别可能代表了演化序列，大云中的完整统计数据使我们第一次能够估计单个星系的整个演化时间尺度。这些结果得到了国际社会的高度评价，在过去的几次国际会议上，包括2005年的原恒星和行星V，都曾就这一主题进行过几次受邀的演讲。

This research aimed at revealing the physical process of star formation in galactic evolution with an emphasis on the possible role of supershells. The method we employed was to make a detailed study of molecular clouds and star formation in the three galaxies of the Local group, the Milky Way, and the Large and Small Magellanic Clouds. We have revealed unprecedented details of the evolutionary scheme of molecular clouds on a galactic scale and conclude that the role of supershells is not dominant as compared with the other processes including stochastic turbulent compression.In the course of this research, we first showed that the Large Magellanic Cloud is the most reliable galaxy among the three, because the other two have much smaller number of samples with significance, around only 20-30, due to the contamination or the less active star formation. The Large Magellanic Cloud on the other hand has nearly 200 samples that allowed to make significant comparison with signs of massive star formation. We used observational data on HII regions and young star clusters taken elsewhere to identify massive star formation in the individual molecular clouds to reveal the three classes of molecular clouds, (1)starless, (2)with HII regions only and (3)with clusters and rich HII regions. These three classes likely represent the evolutionary sequence and the complete statistics in the Large Cloud allowed us to estimate the whole evolutionary timescale for the first time in a single galaxy.These results are highly evaluated in the international community and several invited talks were given on the subject in the past international meetings including Protostars and Planet V in 2005.