%0 Generic
%A Rugel, Michael Rainer
%D 2018
%F heidok:25712
%R 10.11588/heidok.00025712
%T On the formation and destruction of molecular clouds with the Galactic plane survey THOR
%U https://archiv.ub.uni-heidelberg.de/volltextserver/25712/
%X This thesis investigates the properties of molecular clouds with THOR (The HI, OH and Radio Recombination Line (RRL) survey of the Milky Way). We analyze OH absorption at 18 cm within THOR and follow-up observations. We derive the abundance with respect to molecular hydrogen and the total number of hydrogen nuclei: 1) We find a decreasing OH abundance with increasing column density of molecular hydrogen. 2) Due to significant column densities of atomic hydrogen at low N_OH, the OH abundance with respect to N_H is approximately constant. 3) We detect OH components which are associated with gas that is not predominantly molecular or even CO-dark. We conclude that OH is a potential tracer for diffuse gas. Regarding the impact of star clusters on  molecular clouds, we detect signatures of feedback in RRL emission in the star forming region W49A. A comparison to the WARPFIELD models (one-dimensional models of feedback-driven shells) indicates that feedback is not yet strong enough to disperse its molecular cloud and that the shell is either in process of re-collapsing to initiate a new event of star formation or has already re-collapsed. This suggests that at least parts of the star formation in W49A is regulated by feedback.