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    Uncovering and Understanding the Hidden Globular Cluster System of NGC 5128 at Large Radii

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    Author
    Hughes, Allison
    Issue Date
    2022
    Keywords
    galaxy evolution
    galaxy mass
    globular star clusters
    optical identification
    Advisor
    Sand, David
    
    Metadata
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    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Embargo
    Release after 12/28/2022
    Abstract
    The Lambda+Cold Dark Matter cosmological model of the universe is successful at replicating the large scale distribution of galaxies, but fails to match observations at smaller, galaxy scales. In order to match theory with observation, the substructure properties of more galaxies with a variety of properties and environments must be measured. Fully understanding the galaxy NGC 5128 will provide a unique counterpoint to galaxies in the Local Group - it is a giant elliptical galaxy in a dense environment with evidence of merger events. In Chapter 2 I describe a new technique that connects data from the Gaia space telescope with ground-based observations to identify globular cluster (GC) candidates associated with NGC 5128 out to R~150 kpc. I present a new catalog of GC candidates, ranked based on the likelihood that they are true GCs and highlighting those candidates that should be the highest priority for spectroscopic follow-up for confirmation. Additionally, I revise the estimate of the total expected GC population size and show that a substantial number of sources previously argued to be low-velocity GCs are instead foreground stars, bringing the mean velocity and velocity dispersion of the GC system more in line with the galaxy as a whole. This work was published in Hughes et al. 2021. In Chapter 3 I verify my GC candidate selection technique by collecting a large sample of spectra using Magellan/M2FS and AAT/AAOmega. I present new radial velocity measurements for 173 previously known and 125 newly confirmed GCs in NGC 5128. I identify GCs with clear kinematic trends that are associated with halo substructure visible in red giant branch star maps of the galaxy. I examine the systemic velocity, the projected rotation amplitude and axis, and the projected velocity dispersion of the GC system as functions of galactocentric radius, metallicity, and substructure association.Using the updated population of GCs as tracer particles, I make new estimates of the total mass of the galaxy at a variety of radii. These findings further indicate that NGC 5128 formed via hierarchical merging over other methods of formation, such as major merging at late times.
    Type
    text
    Electronic Dissertation
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Graduate College
    Physics
    Degree Grantor
    University of Arizona
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