Role of galactic gaseous halos in recycling enriched winds from bulges to disks: A new bulge-disk chemical connection

We demonstrate for the first time that gaseous halos of disk galaxies can play a vital role in recycling metal-rich gas ejected from the bulges and thus in promoting the chemical evolution of the disks. Our numerical simulations show that metal-rich stellar winds from bulges in disk galaxies can be accreted onto the thin disks owing to hydrodynamical interaction between the gaseous ejecta and the gaseous halos, if the mean densities of the halos (ρ_hg) are as high as 10^-5 cm^-3. The total amount of gas that is ejected from a bulge through a stellar wind and then accreted onto the disk depends mainly on ρ_hg and the initial velocity of the stellar wind. About 1% of gaseous ejecta from bulges in disk galaxies of scale length a _d can be accreted onto disks around R 2.5a _d for a reasonable set of model parameters. We discuss these results in the context of the origin of the surprisingly high metallicities of the solar neighborhood disk stars in the Galaxy. We also discuss some implications of the present results in terms of chemical evolution of disk galaxies with possibly different ρ_hg in different galaxy environments.