Abstract The luminosity function of a star cluster evolves markedly during the pre-main sequence phase. With an assumed initial mass function and premain sequence tracks, we calculate a set of monochromatic luminosity functions which, when compared with observations, can be used to infer the age and star formation history (coeval versus intermittent) of a star cluster. Applied to the Trapezium cluster, our model suggests an age close to a million years, whereas in IC 348 the age estimate yields 4-6 million years and continual bursts of star formation seem to have occurred in this cluster, CCD imaging observations in the I-band are presented for NGC 663, for which an age of 10-30 million years is inferred. The initial mass function for NGC 663 in the range 2-7.1 M⊙ has a slope of -0.77 ± 0.20, much shallower than that for the solar neighborhood field stars. We interpret this being due to mass segregation in the cluster. We interpret this as being due to mass segregation in the cluster.
- Luminosity function
- Young star cluster