Galaxy Metal Abundance And Chemical Evolution

To assess the possible systematic differences among different oxygen abundance indicators and understand the origin of nitrogen and the star responsible for nitrogen production, we study two star-forming galaxy samples in this thesis: one is the strong emission line galaxy sample, selected from DR3 of the Sloan Digital Sky Survey (SDSS), the other is a blue compact galaxy sample(BCGs), basing on our high-quality ground-based spectroscopic observations from 2.16 m telescope at the XingLong Station of the National Astronomical Observatory of China.For each sample, the electron temperature(T_e) and electron density (n_e), and then the oxygen abundance from T_e-method are determined reliably. At the same time, oxygen abundance from strong line metallicity indicators, such as R₂₃, P, N2, and O3N2, are also calculated. We also compared oxygen abundance of star-forming galaxies obtained with the T_e-method, R₂₃-method, P-method , N2-method, and O3N2-method.For blue compact galaxies, we found that the oxygen abundance covers the range 7.15 < 12 + log(O/H) < 9.0; nitrogen is found to be mostly a product of secondary nucleosynthesis for 12 + log(O/H) > 8.2 and apparently a product of primary nucleosynthesis for 12 + log(O/H) < 8.2. The oxygen abundances derived from the T_e method are systematically lower by 0.1-0.25 dex than those derived from the strong line empirical abundance indicators, consistent with previous studies based on H II region samples. The existence of the metallicity-luminosity relation in BCGs over a large range of abundances and luminosities are confirmed. Our sample of galaxies shows that the slope of the metallicity-luminosity relation for the luminous galaxies ( -0.05) is slightly shallower than that for the dwarf galaxies (～—0.17). An offset was found in the metallicity-luminosity relation of the local galaxies and that of the intermediate redshift galaxies. It shows that the metallicity-luminosity relation for the emission line galaxies at high redshift is displaced to lower abundances, higher luminosities, or both.For the starburst galaxies in the SDSS DR 3, we found that the oxygen abundances derived from the T_e method are systematically lower by ～0.2 dex than those derived from the R₂₃ method, consistent with previous studies based on H II region samples. A small offset for oxygen abundance was found between T_e-method and P-, N2-, O3N2-method. When we studied the relation between the N/O and the...