H$_\gamma$ and H$_\delta$ absorption lines and the Initial Mass Function in extragalactic star forming regions

Abstract

Abstract. High-dispersion, long-slit spectroscopic observations of 13 extragalactic star-forming regions were obtained for two Blue Compact Dwarf galaxies (IZw18, IZw36) and for bright star-formation regions in the spiral galaxies M 101 and M 51 and in the irregular starburst galaxies Mrk 171 and NGC 4449. The H γ and/or H δ absorption lines have been observed in 11 star forming regions and will be used to constrain the Initial Mass Function and age of the young stellar populations. In this paper we present the results of the observations and the measurements of the absorption and emission lines. The astrophysical discussion is deferred to a forthcoming paper.