Böttner, Christoph: Dense Cores in Galactic Cirrus Clouds. - Bonn, 2005. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5N-05685
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5N-05685,
author = {{Christoph Böttner}},
title = {Dense Cores in Galactic Cirrus Clouds},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2005,
note = {In this thesis I study the formation and evolution of dense cores in cirrus clouds. Cirrus clouds are diffuse and translucent molecular clouds widely spread within the galaxy. Dense cores in molecular clouds are the locations of the origin of star formation. The knowledge of how cores form and how they evolve is the key to understand the initial conditions of the star formation process. Especially the starting conditions are still poorly known, despite recent progress. Studies of cores in various regions with different physical conditions will help to assess the important processes within the formation and evolution of these cores. A fair number of investigations have already been made towards regions with known star formation. However, there the processes are often more complicated by the feedback actions of new-born or young stars. Translucent cirrus clouds, on the other hand, are relatively simple and quiescent objects, dominated mostly by turbulent gas motions. Due to the lack of active star formation they are thought to show a more simple behaviour than many of the dark molecular clouds. The investigation of cirrus cloud cores could therefore help to reveal the importance of particular conditions and events.
Using the IRAM 30-m radio telescope and the bolometer arrays I observed a small sample of 5 dense cores in cirrus clouds in the thermal dust continuum. The dust continuum emission appears to be one of the best tracers of the H2 column density and is particularly suited to locate and map the core regions. However, it does not provide any kinematic information and hence no access to the kinetic energy in the cores. Additionally, I observed the cores with the FCRAO 14-m radio telescope in the CS (2 → 1) transition, and several other molecular lines with the IRAM 30-m telescope. Molecular line observations provide kinematic properties, but because of abundance variations they are often difficult to interpret. Hence, the gas chemistry in the core becomes important and has to be considered. Together, these data provide the possibility to obtain a more realistic view of the core properties. I calculate core parameters and analyse the physical conditions. A comparison of cores in cirrus clouds with cores in star-forming regions and dark clouds shows the similarities but also some important differences. One particular core is observed in even more detail using the Plateau de Bure and the OVRO interferometer in CS and HC3N. These data reveal most interesting insights into the core sub-structure and demonstrate the need for observations with high spatial resolution. The star-forming ability of the studied cores is discussed, together with the question if cirrus clouds are able to form stars at all.},

url = {http://hdl.handle.net/20.500.11811/2296}

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