Universität zu Köln

Aghababaei, Atefeh ORCID: 0000-0002-0881-6042 (2023). Kinematics and Structure of Massive Star Formation in NGC 6334-V. PhD thesis, Universität zu Köln.

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Abstract

How filamentary molecular clouds fragment into star-forming hub clusters remains an unresolved issue. This thesis focuses on the observational studies of the massive hub protocluster NGC 6334-V, which is embedded within the filamentary cloud NGC 6334. It delves deeply into the mechanisms operating at three distinct scales: compact structures present within the hub cluster, the sub-pc scales characterizing the filamentary accretions toward the cluster, and the pc scales dynamics defining the relationship between the cluster and the entire molecular cloud. The primary observational data used in this work consists of spectral-line ALMA observations with a spatial resolution of 1800 au, sensitive to both the 3 mm continuum emission and various molecular species. Moreover, low-resolution ancillary observations at larger scales and different wavelengths are also utilized to compare and connect the sub-pc and pc scale filamentary structures, as well as to search for ionized gas. High-resolution ALMA observations reveal 28 compact cores in the central hub cluster NGC 6334-V of which four show a detection of IR compact source counterparts. The existence of young high-mass cores suggest that cluster NGC 6334-V is in an early stage, and the observed segregation among the cores suggests that primordial segregation could be a potential formation scenario. The rotational temperature of CH3CCH varies widely, ranging from a few tens of kelvin up to 252K at the position of the hot core, with a measurement error of ≈20−50K. Utilizing dense gas tracers, particularly H13CO+, six prominent filaments were identified. The central cluster exhibits a distinctive widespread SiO emission, with an exceptionally narrow linewidth of less than 1.8 km s−1. The analysis of the SiO (2–1) line profile and spatial distribution reveals that 99.8% of SiO emission has a width of less than 10 km s−1 and 57% has a width of less than 1.8 km s−1. This emission reveals a tail-like structure along three filaments and suggests that the SiO emission in NGC 6334-V primarily results from low-velocity shocks. These shocks could originate from the encounter of filaments with the high-density central hub or from the confluence of an H II region behind the cluster. The morphological analysis of cluster NGC 6334-V on a large scale suggests a formation scenario based on the ionization injection process from cavities behind the cloud. In this scenario, ionized gas ejected from an unknown source behind the cloud hits the cloud from one side, effectively isolating source V from the rest of the NGC 6334 cloud and pushing the filaments to the opposite side while the accretion continues toward the center.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Aghababaei, Atefeh atefeh.aghababaei90@gmail.com https://orcid.org/0000-0002-0881-6042 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-730409
Date:	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:	Natural sciences and mathematics
Uncontrolled Keywords:	Keywords Language High Mass Star Formation English Star Formation English Interstellar Medium English Hub-Filament Systems English Star Cluster formation English Filament Formation English Shock Gas English ALMA Observations English Accretion English
Date of oral exam:	20 October 2023
Referee:	Name Academic Title Schilke, Peter Prof. Dr. Fuller, Gary Prof. Dr. Zilges, Andreas Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/73040