On the past star formation in the solar neighbourhood

The present day mass function (PDMF) is derived from the data material of the immediate solar neighbourhood. From the comparison of the lower mass part (M < M/sub sun/) and the high mass part of the PDMF it is estimated that the mean past star formation rate related to the present one is in the range 0.08 - 2.0, supposed the initial mass function (IMF) is time independent. References to probable time dependences of the IMF are summarized. Using the PDMF as a constraint on the temporal variation of the IMF, unplausibilities for the star formation rate result if the IMF monotonously flattens in time uniform over the whole mass range. (author)