ABUNDANCE GRADIENTS IN THE STAR-FORMING VISCOUS DISK AND CHEMICAL-PROPERTIES OF THE BULGE

Radial abundance profiles in galaxy disks are predicted in the framewo rk of the chemical evolution of star-forming viscous disk. Using new c alculations of heavy-element yields from Type Ia and Type II supernova e, the oxygen and iron abundances as well as the oxygen-to-iron abunda nce ratio are derived as a function of radial distance away from the g alaxy center, and the results are compared with recent observations in the Galactic disk. The main prediction of the viscous disk model is t hat both alpha- elements and iron-peak elements exhibit a small, simil ar gradient for either stars or gas. We also examine to what extent th e bulge is regarded as an inward extension of the disk from a viewpoin t of chemical properties. The viscous disk model with a Salpeter initi al mass function of stars is found to account for the observed metalli city distribution of K-giant stars in the Galactic bulge.