Galaxy abundance gradients

The existence of abundance gradients of N/O in spiral galaxies imposes limits on the efficiency of HBB since for large efficiencies they would vanish [3,1],... 

Some of these problems are addressed in the inverse wind scenario of Pipino and Matteucci (2004), in which they allow for inflow and assume ad hoc that, the higher the mass of the galaxy, the shorter the infall and especially the star formation timescales. This makes the more massive objects older, in the sense that star formation is stopped by a terminal wind at earlier times, permitting enhanced metallicities and a/Fe ratios in the framework of the classical Salpeter(O.l) IMF. Abundance gradients within elliptical galaxies are reproduced within their very considerable uncertainties by an outside-in scenario in which star formation... 

Trends in emission lines from HII regions in Scd galaxies as a function of galactocentric distance interpreted by L. Searle as a consequence of large-scale abundance gradients. 

Abundance gradients in disk galaxies constitute one of the more important observational constraints for models of galaxy chemical evolution. As a matter of fact, abundance gradients were first recognized to exist in external galaxies, where radial trends of emission line ratios were noted as far back as in the fourties (Aller 1942) and were attributed to abundance gradients in the early seventies (Searle 1971, Shields 1974). 

Maciel Koppen (1994) have examined whether abundance gradients in the Galaxy steepen with time, by comparing the gradients from Type I, Type II and Type III PNe. The evidence is marginal. 

The spatial distribution of abundances in galaxies depends coarsely on the Hubble type. Spectroscopic study of H II regions in unbarred or weakly barred spiral galaxies typically reveals a strong radial gradient in metallicity (Figure 8), as determined from O/H (Zaritsky, Kennicutt, Huchra 1994 ZKH Vila-Costas Edmunds 1992 VCE). The... 

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