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| Identifier |
000408226 |
| Title |
Structure and evolution of magnetic molecular clouds : observational consequences and tests |
| Alternative Title |
Αξιολογώντας το ρόλο των μαγνητικών πεδίων στην αστρική γένεση |
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Author
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Πανοπούλου, Γεωργία Βιργινία
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Thesis advisor
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Τάσσης, Κωνσταντίνος
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Reviewer
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Χαρμανδάρης, Βασίλειος
Κυλάφης, Νικόλαος
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| Abstract |
Molecular clouds provide the initial stage for the star formation process. A complete
understanding of the onset of this process relies on studying the numerous physical mechanisms that
influence the structure and evolution of molecular clouds.
Detailed maps of cloud structure have recently been delivered by the Herschel Space Observatory,
through observations of thermal dust emission. These measurements show that molecular cloud morphology is predominantly filamentary. The filamentary structures seem to have a ‘characteristic’ width
of 0.1 pc. However, a robust theoretical explanation for this characteristic scale has proved elusive. We
highlight discrepancies between this result and other observational evidence. Using an own-developed
automated code for measuring filament properties, we revisit the analysis of filament widths on Herschel images. We find biases in the adopted methodology of previous works and show that the available
data do not support the existence of a ‘characteristic’ width for the observed filaments.
Filament orientations appear to be closely related to that of the magnetic field within dense star-
forming clouds. The observed connection suggests that the field is dynamically important in such
systems. Similar evidence is lacking in the regime of translucent molecular clouds. We investigate
the situation in this poorly studied regime, targeting the Polaris Flare molecular cloud. We map the
magnetic field orientation in the cloud using the RoboPol optopolarimeter and deliver upgrades to the
existing data processing pipeline (improving control of systematics throughout the instrument field of
view). We find the field to be ordered across a large fraction of the cloud area, implying that it is
strong compared to gas turbulent motions. We compare the orientation of the observed magnetic field
to that of filaments in the Herschel map of the cloud and find strong preference for alignment. Our
results indicate that the magnetic field has an important impact on the dynamics and therefore the
structure and evolution of this cloud.
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| Language |
English |
| Subject |
Interstellar medium |
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Magnetism |
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Star formation |
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Αστρογέννεση |
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Διαστρικό μέσο |
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Μαγνητισμός |
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Μοριακά νέφη |
| Issue date |
2017-04-03 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Physics--Doctoral theses
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Type of Work--Doctoral theses
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| Views |
1213 |
Structure and evolution of magnetic molecular clouds : observational consequences and tests
