Abundance gradient in interstellar medium

Abstract

The author discusses in this review the implication of observed abundance gradient in the interstellar medium on the chemical evolution of the galaxy. I describe the ingradients that are required to develop enrichment model and also the predications of different model on the variation of metallicity in the galactic disk. The observed abundance gradient derived by various workers using different kind of objects are also summarized. A few other observations that are relevant to the problem of chemical evolution – like the G dwarf problem and the abundance ratio of the elements formed by primary and secondary processes of Nucleosynthesis – are also briefly discussed. Some of the advanced models of chemical evolution that are able to account for all these observations are described. It is necessary to extend the metallicity survey to the outermost parts of the galactic disk since there is evidence that the chemical evolution of these parts has been radically different from that of the solar neighbourhood. The additional constraint impose by such observations would lead to a more comprehensive theory of the chemical evolution of the galactic disk.