In order to study the star formation history of dwarf irregular galaxies, we have obtained B and V photometry of 2250 stars down to a limiting magnitude B = 24.5 on CCD images of two regions in the Local Group galaxy WLM. The resulting colour-magnitude diagrams have been compared with synthetic diagrams generated with the aid of a simulation code based on theoretical models of stellar evolution. A significant difference is found between the star formation activities in the two regions, one of which (Region 1) shows a young population due to star formation processes which stopped a few million years ago; this population is totally absent in Region 2. Both regions have an underlying population at least 109 yr old, apparently born during a long-period, low-intensity, star formation activity, whilst the recent star formation in Region 1 can be either a burst episode or the final phase of a more continuous phenomenon. This activity cannot have lasted for all the galaxy's lifetime. The luminosity functions of the stars in the two regions are consistent with those obtained for other irregulars. A Salpeter's Initial Mass Function (IMF) is in good agreement with the observed data both for the luminosity functions and the colour–magnitude diagrams as well as the inferred metallicities, whilst steeper and flatter IMFs provide results which are markedly less consistent with these data.
No takes yet. Share an insight, caveat, or question.
Ferraro et al. (1989) studied this question.