Universität zu Köln

Sadaghiani, Mahya (2021). Unveiling the properties of the clusters in the NGC6334 filamentary cloud including the physics of shocked gas and accretion. PhD thesis, Universität zu Köln.

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Abstract

NGC6334 is a nearby high-mass star-forming complex that has been the target of multiple studies at different wavelengths. This filamentary cloud contains several massive protoclusters at different stages of evolution which are likely pinpointing sites of high mass star formation activity. In order to investigate the kinematics of the dense gas at the scales of the clusters (<1 pc), we conducted ALMA observations towards the two high-mass protoclusters NGC6334-I and NGC6334-I(N) embedded in the filamentary star-forming complex NGC6334, as well as the gas connecting them to the large-scale filament. The observations cover the spatial scales from 1800 au to 0.25 pc and are sensitive to the 3 mm continuum emission and different molecular species. The intensity maps of dense gas tracers reveal a network of filamentary structures converging at the positions of these two clusters. The analysis of the velocity fields results in similar mass accretion rates for both clusters, suggesting that they are competing for the mass reservoir in the main filament. The ALMA continuum map at 3 mm revealed a total of 142 cores in the observed region. The compact cores are grouped in four main clusters identified by machine learning algorithms. The typical separations (4000-12000 au) together with the core masses (0.2-100 Msun) are in agreement with turbulent fragmentation at scales of 0.1 pc. We find that the CMF of the clusters show an excess of high-mass cores compared to the IMF, which can be due to effect of temperature and the unresolved multiplicity. The evidence of mass-segregation is found in NGC6334-I and NGC6634-I(N) with locating the massive cores close to the center. The accretion process via the filamentary network possibly generates slow shocks due to the transport of material. On the other side, a large population of star-forming cores can produce high-velocity shocks due to the outflows. The SiO emission map obtained with ALMA is an ideal tracer of shocked gas and exhibits a complex morphology with a broad variety of line profiles and a large number of overlapping emission features towards the clusters NGC6334-I and NGC6334-I(N). As an attempt to decompose the slow shocks from the high-velocity shocks, I took advantage of spectral decomposition and wavelet analysis. The spectral decomposition separates the two types of shocks based on the width of the SiO line profile. The complex wavelet analysis isolates the slow shocks based on the probability density function (PDF) of their wavelet coefficients. The decomposition analysis reveals that 30% of the shock energetics in the region are generated in slow shocks, while for the remaining 70%, outflows are responsible. The widespread emission generated by slow shocks dominates at scales >0.1 pc.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Sadaghiani, Mahya sadaghiani.mahya@gmail.com UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-530847
Date:	24 August 2021
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 High mass start formation English Cluster properties English Accretion English Shocked gas UNSPECIFIED Filaments UNSPECIFIED sub-mm observations UNSPECIFIED ALMA observations UNSPECIFIED Astrophysics UNSPECIFIED Start formation UNSPECIFIED Interstellar medium UNSPECIFIED
Date of oral exam:	31 August 2020
Referee:	Name Academic Title Schilke, Peter Prof. Dr. Röllig, Markus Priv. Doz. Dr. Saur, Joachim Prof. Dr. Sanchez-Monge, Alvaro Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/53084