A NEW APPROACH TO DETERMINE THE INITIAL MASS FUNCTION IN THE SOLAR NEIGHBORHOOD

Oxygen to iron abundance ratios of metal-poor stars provide informatio n on nucleosynthesis yields from massive stars that end in Type II sup ernova (SN II) explosions. Using a standard model of chemical evolutio n of the Galaxy we have reproduced the solar neighborhood abundance da ta and estimated the oxygen and iron yields of genuine SN II origin. T he estimated yields are compared with the theoretical yields to derive the relation between the lower and upper mass limits in each generati on of stars and the initial mass function (IMF) slope. Independent of this relation, we furthermore derive the relation between the lower ma ss limit and the IMF slope from the stellar mass-to-light ratio in the solar neighborhood. These independent relations unambiguously determi ne the upper mass limit of m(u) = 50 +/- 10 M-. and the IMF slope inde x of 1.3-1.6 above 1 M-.. This upper mass limit corresponds to the mas s beyond which stars end as black holes without ejecting processed mat ter into the interstellar medium. We also find that the IMF slope inde x below 0.5 M-. cannot be much shallower than 0.8.