Chemical enrichment by Wolf–Rayet stars: non-solar metallicities

Following on from our recent Paper I, we present theoretical models of Wolf–Rayet (WR) stars for non-solar metallicities from   Z = 0.03  to 0.0001 by mass fraction with different mass-loss rate assumptions. We find that some single WR stars may still form even at the lowest metallicities, but whether this occurs or not depends critically on the upper cut-off point of the initial mass function used. As at solar metallicity, a population of binaries is required to fully reproduce WR star observations. For most scenarios, these binaries dominate the low-metallicity WR population but probably not the enrichment. We find comparable carbon enrichment from single WR stars to that from asymptotic giant branch stars at all metallicities for which data are available, but which of them is the dominant source of carbon depends strongly on the set of asymptotic giant branch yields adopted and the assumed initial mass function. We find an increase in carbon enrichment with increasing metallicity but a decrease in oxygen enrichment, as confirmed by observation.