Redetermination of the helium abundances in HII regions in Blue Compact Dwarf Galaxies

Abstract

The He/H abundances in HII regions in Blue Compact Dwarf Galaxies are redetermined using the new recombination coefficients of Benjamin et al. The electron number density ne in the He+ region, optical depth τ3889 in the HeI λ3889 A line, and coefficient of underlying stellar absorption aHeI are determined using the self-consistent method of Olive and Skillman. The primordial helium abundance and its enrichment are found using the helium abundances obtained in this paper and heavy-element abundances from our recent paper I: Yp = 0.244 ± 0.004 and dY/dZ = 8.8 ± 4.6.