Multiple Velocity Component Analysis of Ammonia Spectral Lines in High-Mass Star-Forming Regions

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.

Department dc:contributor.department

Physics, Engineering Physics and Astronomy

Year dc:date.issued

2025

Author dc:creator

• Withers, Tai

Advisor dc:contributor.supervisor

• Sadavoy, Sarah

• Astronomy
• Astrophysics
• Physics
• Star Formation

Statement dc:rights

• Attribution-ShareAlike 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-sa/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1974/34296

OAI identifier oai:identifier

oai:queensu.scholaris.ca:1974/34296