银盘边缘的分子云

Molecular clouds in the Extreme Outer Galaxy (EOG) not only delineate the spiral structure and warping of our Galaxy, but they also serve as an excellent laboratory for studying the star-formation process in a physical environment that is very different from that of the solar neighborhood. However, because of the far distance and warping involved, and the lack of surveys with the combination of high-sensitivity, wide velocity and latitude coverage in the past, the molecular clouds detected in the EOG are less than 30, and even more the star formation signatures are only revealed in few of these dense cores. The high-sensitivity data from Milky Way Imaging Scroll Painting (MWISP) survey will provide us a unique opportunity to study the EOG clouds. Recently, we have detect about 300 EOG clouds, their properties are different from those of the molecular clouds in the inner Galaxy that with different Galactic environments. The distribution of the EOG clouds delineates a new segment of spiral arm. However, our current researches are within a limited Galactic range. The broad range of EOG regions still remain unknown. In addition, only depends on MWISP data, the properties of the EOG clouds are far from being determined. Combining multi-transition CO and its isotopic data, dense gas tracers, methanol, and water maser data, and WISE archive data, this project will research on the identification of EOG clouds, the properties, and star-formation of EOG clouds, and the 3-dimentional structure of the spiral structure they may traced.

银盘边沿的分子云即EOG分子云不仅定义了银盘的大小和盘的扭曲，描绘盘上的气体旋臂结构,还是研究低密度和低金属丰度环境下恒星形成的理想场所。但由于距离远和翘曲,对巡天的灵敏度，速度和银纬覆盖要求较高,过去巡天项目发现的EOG分子云不足30个，证认出有恒星形成的分子云共2个。高灵敏的”银河画卷计划”,为系统地研究EOG分子云提供了机遇。利用该数据我们近年发表了近300个EOG分子云表，它们显示出与内盘分子云不一样的性质，同时描绘了银盘边缘的一段新旋臂，但我们只对很小的银经范围开展了研究，其它区域的EOG分子云还未知。同时仅依赖于13.7米望远镜的CO数据，我们很难准确定出它们的性质。本项目将利用CO及其同位素多能级跃迁，致密分子气体探针，甲醇脉泽，水脉泽，以及其它波段巡天数据如WISE，开展EOG分子云证认和性质研究，EOG分子云中的恒星形成以及这些分子云可能示踪的气体旋臂的三维结构研究。

银盘边缘的分子云即EOG分子云不仅定义了银盘的大小和盘的扭曲，描绘盘上的气体旋臂结构,还是研究低密度和低金属丰度环境下恒星形成的理想场所。但由于距离远和翘曲,对巡天的灵敏度，速度和银纬覆盖要求较高,过去巡天项目发现的EOG分子云不足30个，证认出有恒星形成的分子云共2个。高灵敏大天区覆盖适度高空间分辨率的”银河画卷计划”数据为研究EOG分子云提供了新的机遇，我们发现银河画卷数据在银盘边缘区域探测到的分子气体的总流量是分别是哈佛史密松天体物理中心1.2米和五大学天文台14米望远镜巡天的43.8和7.4倍。基于该巡天数据，我们构建了国际上最大的EOG分子云样本，极大地丰富了处于低金属丰度和低密度环境下的恒星形成及演化的研究样本。基于对这些EOG分子云样本的Effelsberg100米和天马65米望远镜的观测，我们在银盘边缘新发现了两个水脉泽，两个甲醇脉泽，一个4765 MHz激发态的OH脉泽，给出了该区域有恒星形成的强有力的观测证据，为未来VLBI视差和自行测量提供了珍贵样本，这些对于后续精确确定银河系旋臂结构有重要作用。对比不同银心距上分子气体性质时，我们还发现银盘边缘分子云的X转换因子明显大于银心距更小的Outer以及Perseus旋臂。银盘边缘的分子气体在垂直银盘方向上的分布相对更宽，翘曲越严重。