Peng, Tzu-Cheng: Galactic massive star forming regions near and far : a (sub)millimeter study of the Orion Molecular Cloud 1 and W49A. - Bonn, 2010. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
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author = {{Tzu-Cheng Peng}},
title = {Galactic massive star forming regions near and far : a (sub)millimeter study of the Orion Molecular Cloud 1 and W49A},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2010,
month = sep,

note = {Massive stars play an important role in shaping the structure of galaxies due to the large energy output during their lifetime. However, because of the short evolutionary time scales, the large extinction toward their birth places, and the large distance of massive stars, our understanding of their formation is still sketchy. Hence, the observations of two well-known massive star forming regions in our Galaxy (W49A at 11.4 kpc and Orion Molecular Cloud 1 at 414 pc) were carried out using the IRAM 30 m and APEX telescopes, including large-scale mappings of various molecular line emission, such as CO isotopologues, HCN, \HCOP, and SiO. The results of W49A show that its starburst was triggered by expanding shells, causing fragmentation that lead to the formation of massive stars. The cause of the shell expansion is not clear, but likely due to the stellar feedbacks from a first generation of young massive stars by strong stellar winds and ultraviolet radiation, or the interaction between stars in a cluster, which is possibly related to the large-scale gas ejections found in the W49 complex with a total kinetic energy of few times 10^50 erg. Apart from W49A, the study in Orion Molecular Cloud 1 reveals a more detailed picture of young massive stars strongly interacting with their local environment. The highly excited CO emission in Orion Molecular Cloud 1 shows two main components: one is the north-south dense ridge where two active star-forming regions (Orion BN/KL and Orion South) are located, and the other one consists of photon-dominated regions (e.g., the Orion Bar and Orion East) spread over the whole area, where gas and dust are heated by ultraviolet photons from the Trapezium cluster. In addition, several outflows are detected in the higher-J transitions of CO, which indicates the important role of shock heating associated with star-forming activities.},
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