Star formation in extragalactic HII regions. Determination of parameters of the initial mas function

A method for using the colors of star-forming complexes to derive the slope and upper mass limit of the initial mass function (IMF) and the age of the complex is proposed in the framework of synthetic evolutionary models of s tar-cluster populations. The star-formation parameters of 105 complexes in 20 spiral and irregular galaxies are determined. The IMF slopes in differen t star-forming complexes differ appreciably, and their dependence on the lu minosities and masses of the complexes is derived. The duration of the star -formation period increases with the luminosity of the complex, and complex es with longer star-formation periods are richer in metals. The slope of th e integrated IMF in a Galaxy depends on the mass spectrum of its complexes, and the upper mass limit of the IMF is lower in early-type spirals. (C) 20 01 MAIK "Nauka/Interperiodica".