SOLAR NEIGHBORHOOD CONSTRAINTS ON VISCOUS MODELS FOR GALACTIC DISKS

We examine the predictions of disc evolution models with viscous flows for the chemical enrichment of the solar neighbourhood. We show that the local age metallicity distribution and stellar abundance distribution is in this case critically determined by the star formation history at large radii. In particular, suppression of star formation in the outermost disc combined with radial flow leads to an input of low-metallicity gas into the solar neighbourhood, with consequences indistinguishable from those of continued infall from the halo. We therefore argue that the chemical data do not necessarily constrain the disc formation time-scale.