Universität zu Köln

Makai, Zoltán Sándor (2015). The physics and chemistry of photon-dominated clouds in NGC 3603. PhD thesis, Universität zu Köln.

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Abstract

High-mass star-formation in the interstellar medium is one of the main open questions in astronomy: high-mass stars are rare, evolve fast and are frequently obscured or located in dense clusters. Most of our knowledge stems from simulations, not from direct observations. Stars are born within molecular clouds due to the perturbations of local physical and chemical processes. To investigate these perturbations, we observed one of the most prominent HII region, NGC 3603, in our Galaxy. This molecular cloud complex embraces an open cluster, with massive and hot stars, which provides strong stellar winds and radiation field. These phenomena heavily interact with the neighbouring environment and govern the local physics and chemistry. To investigate these effects and their influence, we received spectroscopy data of molecules, ions and atoms via Herschel Space Observatory. Data of ground-based telescopes were also used as complementary data. The observational results showed that the observed clouds have gas components with different temperatures as well as vigorous gas movements. Different models were used to fit the observations. We found that the observed line intensities and abundances match with the model predictions and the model results are independent from the cloud geometry. All the results we obtain, give the opportunity to characterize the physical conditions and chemical processes within NGC 3603. Based on our observations and our model calculations, we concluded that the observed molecular clouds (or part of them) are probably in gravitationally unstable stage. Hence, the star-formation process within NGC 3603 is still ongoing. This scenario is in agreement with previous studies. It is also likely, that the observed clouds do not rotate as a rigid rotor but have a torsional geometry. On the other hand, due to observational facts (e.g., large beam size, distance of NGC 3603), we were only be able to make statements about the chemistry/chemical stratification within certain limits.

Item Type:	Thesis (PhD thesis)
Translated abstract:	Abstract Language Die Entstehung massereicher Sterne ist eine der großen offenen Fragen moderner Astronomie. Massereiche Sterne sind selten, entwickeln sich schnell und sind oft tief in Staub eingebettet oder in dichten Sternhaufen zu finden. Der größte Teil unseres Wissens über massive Sternentstehung stammt daher aus Simulationen und nicht aus direkten Beobachtungen. Lokale Störungen des physikalischen und chemischen Zustandes regen die Bildung von Sternen in Molekülwolken an. Um diese Störungen zu untersuchen beobachteten wir eine der prominentesten HII Regionen innerhalb unserer Milchstraße, NGC 3603. Dieser Molekülwolkenkomplex umgibt einen offenen Sternhaufen heißer massereicher Sterne die starke Sternwinde und intensive Strahlung produzieren. Um deren Einfluß auf die Sternentstehung zu untersuchen, verwendeten wir spektroskopische Beobachtungen des Herschel Weltraumteleskops von Molekülen, Ionen und Atomen. Zusätzlich dazu haben wir komplementäre Daten bodengestützter Teleskope verwendet. Die Daten zeigen, daß die beobachtenen Molekülwolken Gaskomponenten mit verschiedenen Temperaturen beherbergen, die teilweise starke Strömungsgeschwindigkeiten aufweisen. Unsere Ergebnisse erlauben uns die physikalischen und chemischen Zustandsbedingungen innerhalb NGC 3603 zu charakterisieren. Basierend auf unseren Beobachtungen und unseren Modellrechnungen schließen wir, daß die beobachteten Molekülwolken (bzw. Teile von ihnen) gravitativ instabil sind. Folglich ist von einer anhaltenden Sternentstehung in NGC 3603 auszugehen. Diese Annahme wir auch von früheren Studien unterstützt. Es ist weiterhin wahrscheinlich, daß die beobachteten Wolken nicht starr rotieren, sondern eher eine torsionsartige Geometrie aufweisen. Die große Entfernung von NGC 3603 sowie der endlich große Teleskopbeam erlauben uns nur eingeschränkte Aussagen über die chemische Schichtung des lokalen Gases zu treffen. German
Creators:	Creators Email ORCID ORCID Put Code Makai, Zoltán Sándor zoltan.makai@lam.fr UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-61168
Date:	23 April 2015
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics I
Subjects:	Natural sciences and mathematics Physics
Uncontrolled Keywords:	Keywords Language interstellar medium, high-mass star-formation UNSPECIFIED radio astronomy, photon-dominated clouds UNSPECIFIED spectroscopy, molecular clouds UNSPECIFIED
Date of oral exam:	14 October 2014
Referee:	Name Academic Title Stutzki, Jürgen Prof. Dr. Röllig, Markus PD Dr.
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Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/6116