THE OXYGEN YIELD AND THE INFALL HISTORY OF THE SOLAR NEIGHBORHOOD

If the yield of oxygen has not changed significantly during past galactic history and its production is adequately described by the instantaneous recycling approximation, the distribution of oxygen abundance in low-mass stars in the solar neighbourhood together with the present fractional gas content can provide an estimate of the oxygen yield and of the time history of infall to the galactic disc. Use of Pagel's G-dwarf distribution gives a yield of about 80 per cent of the present oxygen abundance and a current infall rate of about a third to a half of the rate at which mass is locked up in stars. If the infalling gas has non-zero oxygen abundance, both the yield and the current infall are reduced, but the infall remains significant. These results are in good agreement with those of a recent solar neighbourhood model by Pagel. If observations suggest that current infall is unimportant, the present yield must be approximately halved but its value must have been significantly higher in early galactic history.