Multiple Velocity Component Analysis of Ammonia Spectral Lines in High-Mass Star-Forming Regions
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Authors
Withers, Tai
Date
2025-01-30
Type
thesis
Language
eng
Keyword
Astronomy , Astrophysics , Physics , Star Formation
Alternative Title
Abstract
High-mass star-forming regions are turbulent and chaotic environments that contain the seeds to produce massive stars. Previous analyses of dense gas in nearby low-mass star-forming regions have identified the presence of multiple coherent velocity structures overlapping along the line of sight. We perform a multiple component analysis of ammonia (NH3) gas observations from a Green Bank Telescope large program covering 11 giant molecular clouds (GMCs). To this end we extended existing codes to enable simultaneous fitting of up to three velocity components with radiative transfer. Using our multiple component fitting technique, we produce the best maps of the centroid velocity and velocity dispersion in these clouds to date. These maps uncover complex line-of-sight velocity features within the densest zones of the GMCs and at the sites of high-mass star formation, providing insight into these regions not previously seen. Further, we utilize the products of our multicomponent modelling to identify and characterize 510 dense clumpy structures which may represent prestellar cores. Using H2 column density and temperature maps, we find that these cores are marginally gravitationally bound, and we further perform a virial analysis accounting for the effect of surface pressures. This secondary analysis highlights the strongly varying nature of our sample. Considering the impact of cloud weight, dense cores are found to be approximately consistent with virial equilibrium with high scatter. For a small sample of cores (42) where we characterize the turbulent surface pressure, we find that this addition results in strong pressure confinement.
Our results show an overall consistency with previous works studying cores in low-mass star-forming regions.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution-ShareAlike 4.0 International