The abundance and chemical evolution of nitrogen in spiral galaxies.
| dc.contributor.advisor | Henry, Richard C., | en_US |
| dc.contributor.author | Thurston, Tad Ralph. | en_US |
| dc.date.accessioned | 2013-08-16T12:29:59Z | |
| dc.date.available | 2013-08-16T12:29:59Z | |
| dc.date.issued | 1998 | en_US |
| dc.description.abstract | The character of nitrogen processing in spiral galaxies is studied in this dissertation. Of particular interest are questions of how the (N/O) ratio changes over time as a result of perturbations of environmental parameters, as well as the importance of primary vs. secondary nitrogen generation and the regimes where one may be the preferred method. A robust numerical chemical evolution code (NICE) was written to model the change in elemental ratios during galactic chemical processing. This code is consistent with standard observational constraints. A new method is developed for the calculation of (N/O) abundances in the absence of observed temperature-diagnostic emission lines. New (N/O) abundances are derived for previously observed HII regions in spiral and dwarf galaxies, and the trends noted in the observations are modeled with the numeric code NICE. I conclude it is likely that early-type spirals once had a higher rate of infalling material relative to late-type galaxies, resulting in both a higher (N/O) ratio as well as a lower gas fraction during later epochs. NICE models also suggest that the star formation rate was suppressed in the extremely metal-poor stages of galaxy chemical processing, as shown by the model fits to the I Zw 18 regions as well as a highly redshifted primeval galaxy. Primary nitrogen production is only realized in stars of 4-8 solar masses, so that this is the first source of nitrogen after an episode of star formation. This is seen in both the observations and the models of low-metallicity dwarf galaxies. At later times, secondary nitrogen is released by stars in the lower mass range (1-4 solar masses), contributing to the steeper slope seen in (N/O) vs. O/H for the more chemically advanced spiral galaxies. | en_US |
| dc.format.extent | x, 171 leaves : | en_US |
| dc.identifier.uri | http://hdl.handle.net/11244/5612 | |
| dc.note | Adviser: Richard C. Henry. | en_US |
| dc.note | Source: Dissertation Abstracts International, Volume: 59-03, Section: B, page: 1157. | en_US |
| dc.subject | Cosmic abundances. | en_US |
| dc.subject | Spiral galaxies. | en_US |
| dc.subject | Physics, Astronomy and Astrophysics. | en_US |
| dc.subject | Nitrogen Evolution. | en_US |
| dc.thesis.degree | Ph.D. | en_US |
| dc.thesis.degreeDiscipline | Homer L. Dodge Department of Physics and Astronomy | en_US |
| dc.title | The abundance and chemical evolution of nitrogen in spiral galaxies. | en_US |
| dc.type | Thesis | en_US |
| ou.group | College of Arts and Sciences::Homer L. Dodge Department of Physics and Astronomy | |
| ou.identifier | (UMI)AAI9826293 | en_US |
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