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The Atomic Interstellar Medium of M33 Open Access


Other title
interstellar medium
molecular cloud
Type of item
Degree grantor
University of Alberta
Author or creator
Koch, Eric W
Supervisor and department
Rosolowsky, Erik (Physics)
Examining committee member and department
Sivakoff, Gregory (Physics)
Morsink, Sharon (Physics)
Pogosyan, Dmitri (Physics)
Department of Physics

Date accepted
Graduation date
2016-06:Fall 2016
Master of Science
Degree level
I present new observations of 21-cm hydrogen line emission from the nearby spiral galaxy M33 (Triangulum) using the Jansky Very Large Array (VLA) in New Mexico. I have spent the majority of the past two years calibrating and imaging these new observations. This was a particularly time-consuming task due to the sheer volume of data, with the final data footprint reaching several terabytes in size. I developed an alternate approach for imaging massive interferometric datasets, which achieves a significant speed-up in computational time by splitting the data into minimally sized chunks. The analysis portion of this thesis focuses on the 21-cm spectral line of atomic hydrogen (HI), which traces the atomic medium. From this I determine the global properties of the atomic interstellar medium (ISM), fit a rotation curve to the galactic disk, and explore the relation between the atomic and molecular media, utilizing existing observations of the 2 to 1 rotational transition of carbon monoxide line. I provide new analysis techniques for determining the co-location of CO(2-1) to the HI emission for spatially resolved studies of the extragalactic ISM. I find similarities in the spectral properties of a narrow ~10 km/s, HI line component, likely arising from cool HI (T~100 K), and the molecular medium traced by CO(2-1). This suggests they trace a similar kinematic portion of the ISM. The average full-width-half-max (FWHM) of the HI filamentary network is 274.1+/-8.8 pc and is a factor of 2.5 times brighter than a large-scale near-constant background component. The filamentary network is predicted to arise from the cool neutral medium (T~100 K), while the large-scale component is consistent with the warm neutral medium (T~10 000 K). Using a novel masking approach to trace the edges of bright HI, namely HI bubbles and wind-driven shells, I show that CO(2-1) emission is preferentially located a distance of ~100 pc from the mask edges and not simply co-located with the brightest HI emission. This suggests that wind-driven shells may play a large role in the formation of molecular clouds in M33.
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
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