The distribution of heavy elements in spiral and elliptical galaxies

In large disk and spheroidal galaxies, spatially resolved abundance informa tion can be extracted by analysis of either emission lines, absorption line s, or both, depending on the situation. This review recaps significant resu lts as they apply to nondwarf galaxies, including the Milky Way, spiral dis ks and bulges, and elliptical and lenticular galaxies. Methods for determin ing abundances are explained in appendices. Conclusions that span the galaxy types treated here are as follows. All gal axies, on average, have heavy-element abundances (metallicities) that syste matically decrease outward from their galactic centers while their global m etallicities increase with galaxy mass. Abundance gradients are steepest in normal spirals and are seen to be progressively flatter going in order fro m barred spirals to lenticulars to ellipticals. The distribution of abundan ces N(Z) versus Z is strongly peaked compared with 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 galax ies. For spiral galaxies, local metallicity appears to be correlated with total (disk+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 me tallicity and secondary processes at high metallicity. Carbon production in creases with increasing metallicity. Abundance ratios Ne/O, S/O, and Ar/O a ppear to be universally constant and independent of metallicity, which argu es either that the initial mass function (IMF) is universally constant or t hat these ratios are not sensitive to IMF variations. In the Milky Way, the re is a rough age-metallicity trend with much scatter, in the sense that ol der stars are more metal poor. In elliptical galaxies, nuclear abundances are in the range [Z/H] = 0.0-0.4 , but the element mixture is not scaled-solar. In large elliptical galaxies [Mg/Fe] is in the range 0.3-0.5, decreasing to approximate to 0 in smaller elliptical galaxies. Other light elements track the Mg enhancement, but th e heavier Ca tracks Fe. Velocity dispersion appears to be a key parameter i n the modulation of [Mg/Fe], but the cause of the connection is unclear.