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Metallicity Map of M33

  • Author / Creator
    Koning, Alice H.
  • I use Keck I spectroscopic observations of 701 Hα sources in the nearby spiral galaxy M33 to determine oxygen, nitrogen, sulfur, and neon abundances in HII regions across the face of the galactic disk. Abundance measurements are obtained with two separate methods (PyNeb and NEAT) through the use of the only known direct metallicity determination method, which relies on detections of weak, temperature-sensitive auroral lines. This data set is approximately double the size of any previous HII region metallicity study in M33. Reliable oxygen abundances are determined for 88 HII regions with PyNeb, and 108 HII regions with NEAT (with significant overlap between the two samples). I investigate the temperature and density distributions, as well as the relation between strong-line metallicity indicators and the metallicity derived from weak auroral lines. I plot radial abundance gradients for [O/H], [N/H], [NII/OII], [S/H], [S/O], [Ne/H], and [Ne/O]. The [O/H] gradient has more scatter than the [N/H] gradient, although both show clear signs of decreasing abundances with increasing galactic radius. The [NII/OII] gradient supports previous evidence that the nitrogen abundance falls off more rapidly than oxygen at larger radii. Conversely, the [Ne/O] gradient indicates that neon falls off more slowly than oxygen at larger radii. The sulfur radial gradient is consistent with a flat slope. I present 2D metallicity maps for [O/H], [N/H], and [NII/OII]. The [O/H] map indicates significant azimuthal fluctuations across the disk of M33, although it is uncertain whether the dominant factor is true azimuthal structure or the relatively large uncertainties on the oxygen abundance measurements. The [N/H] and [NII/OII] abundance maps are much smoother than the [O/H] map.

  • Subjects / Keywords
  • Graduation date
    2016-06
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/R3FF3M741
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. 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.
  • Language
    English
  • Institution
    University of Alberta
  • Degree level
    Master's
  • Department
    • Department of Physics
  • Supervisor / co-supervisor and their department(s)
    • Rosolowsky, Erik (Physics)
  • Examining committee members and their departments
    • Rosolowsky, Erik (Physics)
    • Sivakoff, Gregory (Physics)
    • Sydora, Richard (Physics)
    • Heinke, Craig (Physics)