Mass and age distributions of stars in young open clusters

Abstract

Mass and age distributions of stars, based on homogeneous photoelectric UBV data and reliable cluster membership, are studied in 11 young open clusters. Stellar masses and ages are determined by fitting the theoretical stellar models to each star's position in the HR diagram by means of an interpolation procedure. The main conclusions about the mass function derived from the analysis of seven appropriate clusters are: (1) The slope of the mass spectrum of stars, x in the five young and well populated clusters is approximately the same, the average value being x = 1.4. (2) Contrary to some results on the initial mass function of field stars, no substantial increase in slope for massive stars (say, M greater than 5 solar masses) is found. (3) In general, the clusters under discussion do not show significant variations of mass function slope x with galactocentric distance, although two inner ones have a flat mass function (x = 0.85).