Physical and Chemical State of Cold Cores

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Title: Physical and Chemical State of Cold Cores
Author: Parikka, Anna
Other contributor: Helsingin yliopisto, Matemaattis-luonnontieteellinen tiedekunta, Fysiikan laitos
University of Helsinki, Faculty of Science, Department of Physics
Helsingfors universitet, Matematisk-naturvetenskapliga fakulteten, Institutionen för fysik
Publisher: Helsingfors universitet
Date: 2012
Language: eng
Thesis level: master's thesis
Discipline: Astronomy
Abstract: In this study, I have investigated interstellar molecular clouds and specifically three fields mapped with the Planck satellite and Herschel Space Observatory at radio and sub-millimeter wavelengths: G131.65+9.75, G108.28+16.68, and G161.55-9.30. In these fields, four cloud cores were selected for closer investigation. The molecular line observations at 13CO, C18O, and N2H+ were made with the 20-m radio telescope in Onsala Space Observatory, Sweden. Also, data from Herschel Space Observatory was used. The molecular line observations were used for the study of cloud morphology and kinematics. The hydrogen column densities were estimated from both the molecular line and the dust continuum observations. Radiative transfer models were created for both the continuum and line data. The molecular line emission maxima were approximately where the dust continuum emission maxima were. The molecular line observations indicate that the studied cores are quite stable and show low turbulence. No clear detections of outflows were found in any of the cores. The column densities estimated from the dust continuum observations were 1 - 5 times the column densities derived from the molecular line observations. The column densities derived from the molecular line observations were also considerably lower than what is expected for protostellar cores. When comparing the masses estimated from the molecular line observations to virial and Bonnor-Ebert masses, the mass estimates were considerably lower and it seems that the cores are not on the verge of collapsing. The column density estimates derived from dust emission, however, are in line with the ones expected from prestellar cores and even in the light of the molecular line observations, there is no reason to doubt these data. Clearly, some more research in this area is needed to confirm, for example, the molecular depletion as an explanation of the apparent discrepancy between the continuum and line data
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