Dissertations, Theses, and Capstone Projects

Date of Degree

6-2026

Document Type

Master's Thesis

Degree Name

Master of Science

Program

Astrophysics

Advisor

Julianne Dalcanton

Advisor

Eric Koch

Subject Categories

Astrophysics and Astronomy

Keywords

Galaxies, Neutral Hydrogen, Star-Formation, Local Group, M33, LGLBS

Abstract

The proximity of the Local Group allows for unparalleled resolution of the structure and kinematics of the ISM while simultaneously observing the overall rotation of the galaxy. These nearby galaxies present the opportunity to probe stellar feedback processes in various galactic environments. M33 in particular, offers insight into the nature of the extended neutral gas and its relationship with the star-forming disk and the surrounding CGM, by way of its classic star-forming spiral and relatively undisturbed system. Outside of M33’s distinguished warp, the galaxy offers little evidence of satellites and shows few signs of interaction, begging the question of how isolated galaxies maintain sustainable star formation. From applying global kinematic modeling to new data from the Local Group L-band Survey (LGLBS)–which has the high spatial and kinematic resolution needed to measure signatures of feedback–we uncover a newly resolved filamentary structure along with numerous other extraplanar HI regions in M33. We focus on 21-cm line emission to map the atomic-dominated diffuse interstellar medium (ISM) and present potential origins of the anomalous regions, including both inside and outside of the disk. The numerous off-velocity features within the vicinity of the M33’s star-forming disk, and the filament of 2.9 x 10^6 solar masses can help determine a likely source of sustained star-formation processes. The cohesive 6.59 kpc filament has a linear velocity gradient of 7.23 km/s kpc/s and an accretion rate of 2.15 x 10^-2 solar masses per year that corresponds to a crossing time of 135 Myr. Our results demonstrate how HI surveys of nearby galaxies test how the CGM aids in the galactic recycling necessary for efficient feeding of the star-forming disk, aiding in constraining these processes throughout cosmic time.

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