Universität zu Köln

Zhang, Tianwei (2023). Cloud fragmentation and chemical evolution of the high-mass star-forming region G327.3-0.6. PhD thesis, Universität zu Köln.

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Abstract

In the struggle to understand how stars form in a cluster, it is important to study the morphology, kinematics and chemistry of the star-forming clouds. This thesis focuses on the high-mass star-forming region G327.3-0.6, which is a 3 pc filament at a distance of 3.3 kpc, hosting one hot molecular core and a set of cold dense cores. It was observed with the Atacama Large Millimetre/Sub-millimetre Array (ALMA) at 1.3 mm with high resolution 2". The data were self-calibrated to improve the signal to noise ratio by a factor of 2. The dendrogram algorithm together with the background subtraction were adopted to determine 66 compact cores. Minimum spanning tree determined a median core separation at 0.15pc and possible hierarchical fragmentation, which was supported by the two-point correlation function. Core mass function (CMF) was fitted with an index of -0.83, which is a hint of high-mass star-forming regions. The fragmentation in the filament was dominated by thermal support in small scale (~0.15pc) and by turbulence in large scale (~0.4pc). With toolbox XCLASS, 26 molecules and 39 isotopes were identified in the hot core spectrum, and a temperature of 270K was derived. The temperature error is around 60%. The moment maps were derived for 42 molecular transitions and analyzed by the Histogram of Oriented Gradient (HOG), indicating correlations between DCN and continuum, SiO and H2CO/CH3OH. Principal component analysis (PCA) and clustering algorithm were applied to the average spectra of each core to classify the evolutionary stages. Four groups are found with chemical and physical distinctions, suggesting the excitation temperature of CH3OH to be a good evolutionary indicator. The infrared environment is complex and may associated with photon-dissociation regions (PDRs).

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Zhang, Tianwei twzhang0825@gmail.com UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-709893
Date:	7 September 2023
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics I
Subjects:	Physics
Uncontrolled Keywords:	Keywords Language star formation English astrophysics English astrochemistry English
Date of oral exam:	4 September 2023
Referee:	Name Academic Title Schilke, Peter Prof. Dr. Ossenkopf-Okada, Volker Dr. Saur, Joachim Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/70989