Galaxies with Wolf-Rayet signatures in the low-redshift Universe - A survey using the Sloan Digital Sky Survey

摘要: We have carried out a search for Wolf-Rayet galaxies in all with EW(Hb)>2AA the SDSS DR6. identify features using mixture of automatic and visual classification find total 570 significant (WR) further 1115 potential candidates, several times more than even largest heterogeneously assembled catalogues. discuss detail properties showing focus on their empirical properties. are able to accurately quantify incidence redshift show that likelihood otherwise similar increases increasing metallicity, but WR found wide range morphology. The large sample allows us explicitly there systematic differences metal abundances non-WR galaxies. most striking result is that, below EW(Hb)=100AA, an elevated N/O relative interpret this as rapid enrichment ISM from winds. also model predictions strongly disagree observations at low metallicity; while they do agree quite well data solar abundances. possible reasons models incorporating binary evolution reproduce low-metallicity results reasonably well. Finally we combine nebular He II 4686 12 + log O/H< 8, main sources ionising photons appears be O stars, arguing less dense stellar wind these metallicities, higher WN stars might increasingly dominate ionisation budget.