In large disk and spheroidal galaxies spatially resolved abundance information can be extracted by analysis of either emission lines, absorption lines, or both, depending on the situation. This review recaps significant results as they apply to non-dwarf galaxies, including the Milky Way, spiral disks and bulges, and elliptical and lenticular galaxies. Methods for determining abundances are explained in appendices.Conclusions that span the galaxy types treated here are as follows. All galaxies, on average, have heavy element abundances (metallicities) that systematically decrease outward from their galactic centers while their global metallicities increase with galaxy mass. Abundance gradients are steepest in normal spirals and are seen to be progressively flatter going in order from barred spirals, lenticulars, and ellipticals. The distribution of abundances N(Z) vs. Z is strongly peaked compared to simple closed-box model predictions of chemical enrichment in all galaxy types. That is, a "G dwarf problem", commonly known in the solar cylinder, exists for all large galaxies.For spiral galaxies, local metallicity appears to be correlated with total (disk plus bulge) surface density. Examination of N/O versus O/H in spiral disks indicates that production of N is dominated by primary processes at low metallicity and secondary processes at high metallicity. Carbon production increases with increasing metallicity. Abundance ratios Ne/O, S/O, and Ar/O K

The study of carbon and oxygen abundances yields information on the time evolution and nucleosynthetic origins of these elements, yet they remain relatively unexplored. At low metallicities, (12+log(O/H) < 8.0), nebular carbon measurements are limited to rest-frame UV collisionally excited emission lines. Therefore, we present the UV spectrophotometry of 12 nearby low-metallicity high-ionization H II regions in dwarf galaxies obtained using the Cosmic Origins Spectrograph on the Hubble Space Telescope. We present the first analysis of the C/O ratio in local galaxies based solely on simultaneous significant detections of the UV + O 2 and + C 2 collisionally excited lines in seven of our targets and five objects from the literatureto create a final sample of 12 significant detections. Our sample is complemented by optical SDSS spectra, from which we measured the nebular physical conditions and oxygen abundances using the direct method. At low metallicity, (12+log(O/H) < 8.0), no clear trend is evident in C/O versus O/H for the present sample given the large dispersion observed. When combined with recombination line observations at higher values of O/H, a general trend of increasing C/O with increasing O/H is also viable but with some significant outliers. Additionally, we find the C/N ratio appears to be constant (but with significant scatter) over a large range in oxygen abundance, indicating thatcarbon is predominantly produced by similar nucleosynthetic mechanisms as nitrogen. If true, and our current understanding of nitrogen production is correct, this would indicate that primary production of carbon (a flat trend) dominates at low metallicity, but quasisecondary production (an increasing trend) becomes prominent at higher metallicities. A larger sample will be needed to determine the true nature and dispersion of the relation.

We have compiled a large sample of O, Ne, S, Cl, and Ar abundances which have been determined for 85 galactic planetary nebulae in a consistent and homogeneous manner using spectra extending from 3600-9600Å. Sulfur abundances have been computed using the near IR lines of [S III] λλ9069,9532 along with [S III] temperatures. We find average values, expressed logarithmically with a standard deviation, of log(S/O)=-1.91±.24, log(Cl/O)=-3.52±.16, and log(Ar/O)=-2.29±.18, numbers consistent with previous studies of both planetary nebulae and H II regions. We also find a strong correlation between [O III] and [S III] temperatures among planetary nebulae. In analyzing abundances of Ne, S, Cl, and Ar with respect to O, we find a tight correlation for Ne-O, and loose correlations for Cl-O and Ar-O. All three trends appear to be colinear with observed correlations for H II regions. S and O also show a correlation but there is a definite offset from the behavior exhibited by H II regions and stars. We suggest that this S anomaly is most easily explained by the existence of S +3 , whose abundance must be inferred indirectly when only optical spectra are available, in amounts in excess of what is predicted by model-derived ionization correction factors. Finally for the disk PNe, abundances of O, Ne, S, Cl, and Ar all show gradients when plotted against galactocentric distance. The slopes are statistically indistinguishable from one another, a result which is consistent with the notion that the cosmic abundances of these elements evolve in lockstep.Subject headings: ISM: abundances -planetary nebulae: general -stars: evolution to be both less depleted with respect to solar and uncorrelated with S and Ar, he suggested that the former two elements may be enhanced by nuclear reactions in the PN progenitors through the nuclear processes discussed above, making S and Ar perhaps a better gauge of progenitor composition. Two large optical studies by Aller & Czyzak (1983) and Aller & Keyes (1987) of 41 and 51 galactic PNe, respectively, provided S, Cl, and Ar abundances for many more objects with the suggestion that on the average these three elements tend to have subsolar abundances.While optical spectra permit direct observation of S + and S +2 through the measurement of [S II] λλ6716,6731 and either [S III] λ6312 or the two near IR (hereafter NIR) [S III] lines at λλ9069,9532, photoionization models suggest that S +3

Ultraviolet nebular emission lines are important for understanding the time evolution and nucleosynthetic origins of their associated elements, but the underlying trends of their relative abundances are unclear. We present UV spectroscopy of 20 nearby low-metallicity, high-ionization dwarf galaxies obtained using the Hubble Space Telescope. Building upon previous studies, we analyze the C/O relationship for a combined sample of 40 galaxies with significant detections of the UV O +2 /C +2 collisionally-excited lines and direct-method oxygen abundance measurements. Using new analytic carbon ionization correction factor relationships, we confirm the flat trend in C/O versus O/H observed for local metal-poor galaxies. We find an average log(C/O) = −0.71 with an intrinsic dispersion of σ = 0.17 dex. The C/N ratio also appears to be constant at log(C/N) = 0.75, plus significant scatter (σ = 0.20 dex), with the result that carbon and nitrogen show similar evolutionary trends. This large and real scatter in C/O over a large range in O/H implies that measuring the UV C and O emission lines alone does not provide a reliable indicator of the O/H abundance. By modeling the chemical evolution of C, N, and O of individual targets, we find that the C/O ratio is very sensitive to both the detailed star formation history and to supernova feedback. Longer burst durations and lower star formation efficiencies correspond to low C/O ratios, while the escape of oxygen atoms in supernovae winds produces decreased effective oxygen yields and larger C/O ratios. Further, a declining C/O relationship is seen with increasing baryonic mass due to increasing effective oxygen yields.

We have obtained spectrophotometric observations of 41 anticenter planetary nebulae (PNe) located in the disk of the Milky Way. Electron temperatures and densities, as well as chemical abundances for He, N, O, Ne, S, Cl, and Ar were determined. Incorporating these results into our existing database of PN abundances yielded a sample of 124 well-observed objects with homogeneously determined abundances extending from 0.9 to 21 kpc in galactocentric distance. We performed a detailed regression analysis which accounted for uncertainties in both oxygen abundances and radial distances in order to establish the metallicity gradient across the disk to be 12 + log(O/H) = (9.09 ± 0.05) − (0.058 ± 0.006) × R g , with R g in kpc. While we see some evidence that the gradient steepens at large galactocentric distances, more objects toward the anticenter need to be observed in order to confidently establish the true form of the metallicity gradient. We find no compelling evidence that the gradient differs between Peimbert Types I and II, nor is oxygen abundance related to the vertical distance from the galactic plane. Our gradient agrees well with analogous results for H ii regions but is steeper than the one recently published by Stanghellini & Haywood over a similar range in galactocentric distance. A second analysis using PN distances from a different source implied a flatter gradient, and we suggest that we have reached a confusion limit which can only be resolved with greatly improved distance measurements and an understanding of the natural scatter in oxygen abundances.