Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt.........7s&link_type=abstract
Ph.D. Thesis Johns Hopkins Univ., Baltimore, MD.
Astronomy and Astrophysics
Astronomy
Astrodynamics, Astronomical Models, Chemical Composition, Galactic Bulge, Galactic Evolution, Galactic Halos, Galactic Structure, Galaxies, Dark Matter, Mathematical Models, Metallicity, Radial Flow, Stellar Mass, Supernovae
Scientific paper
I develop theoretical models of the chemical and dynamical evolution of galaxies and present a galactic structure survey-invaluable tools for uncovering the history of the formation of our galaxy. Important advances in my theoretical models are noninstantaneous recycling of newly synthesized elements such as iron from Type Ia supernovae (mergers of white dwarf binaries). I incorporate Type Ia supernovae in models of baryonic dark matter as stellar remnants. If dark halos consist mainly of white dwarfs, as has been proposed, then an excessive supernovae rate is predicted unless the binary fraction was virtually zero. The observed chemical abundance ratios of halo stars signify enrichment from only Type II supernovae. I explore the timescale for the onset of Type Ia supernovae as an upper-limit to the timescale of halo formation. The apparent inconsistency between differences in ages of halo stars (2 to 3 Gyr) and timescale inferred from Type Ia supernovae (approximately less than 0.1 Gyr) suggests galaxies formed from hierarchical substructure. I calculate chemical and dynamical evolution models of viscous disks with noninstantaneous recycling. Patterns of element ratios and scatter in the age-metallicity relationship are predicted throughout the disk. Characterized by radial flows of gas, these models are ideal for exploring new ideas on creating the galactic bulge from disk inflow. The high metallicity of bulge stars may not require an ad hoc variation of the stellar initial mass function if inflow alters the apparent yields in the bulge and solar neighborhood. I present an unbiased, magnitude-limited spectroscopic survey of F-G stars. Radial velocities accurate to approximately less than 10 km/s are derived and compared with predictions of galactic structure models. Distances are derived by photometric parallax, and three dimensional velocities are calculated using published proper motions. Calibration of spectral line strengths against metallicity is presented for standard stars. Evaluation of metallicities of program stars is forthcoming. These data will be useful for constraining the existence of a metallicity gradient in the galactic halo, and determining correlations between kinematics and chemistry in the disk/halo transition.
No associations
LandOfFree
The chemical and dynamical evolution of the galaxy does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The chemical and dynamical evolution of the galaxy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The chemical and dynamical evolution of the galaxy will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1264138