Jarle Brinchmann
CAUP / Leiden University

Abstract
Wolf-Rayet stars are among the most luminous and hottest stars around, but
they are rare: only a few hundred are known in the Milky Way and Magellanic clouds. Since they appear soon after a burst of star formation has taken place they are found in star-forming regions and occasionally there are enough that their signatures can be seen in spectra of galaxies, these are Wolf-Rayet galaxies. In the past only ~200 of these galaxies have been found and usually haphazardly selected.

Here we present a search for WR galaxies in the SDSS and report a study of 570 such galaxies with a further 1115 potential candidates. We will discuss in detail the properties of galaxies showing Wolf-Rayet features with a focus on their empirical properties and discuss how these results provide constraints on stellar evolution models and mass-loss in massive stars. The large sample allows us to show explicitly that there are systematic differences in  the metal abundances of WR and non-WR galaxies.

The most striking result is that below EW(Hbeta)=100Å, Wolf-Rayet galaxies show an elevated N/O relative to non-WR galaxies. We interpret this as a rapid enrichment of  the ISM from WR winds. We also show that the model predictions for WR features are in strong disagreement with the observations at low  metallicity and argue that this point to a significant contribution of binaries to the production of Wolf-Rayet stars.

2008 April 30, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto