Hydrogen absorption line profiles of ionizing star clusters

Abstract

Model synthesized profiles of the Balmer absorption lines for ionizing star clusters have been constructed for different ages ranging from 1 to 40 Myr and power-law initial mass functions (IMF) of different slopes. These profiles can be used in combination with those corresponding to different stellar populations in order to reproduce the profiles observed in regions of recent star formation and eliminate the effect of contamination of the nebular emission lines by the underlying stellar absorption. It is found that the computed profiles are rather insensitive to both age and assumed IMF. The widest profiles correspond to an age of 4 Myr and a solar neighbourhood IMF and the narrowest to ages of about 8–9 Myr and a value of the IMF slope of about 1.35.