Résumé / Abstract Seminaire_IAP
« Wolf-Rayet galaxies at high and low redshift: When individual stars make an impact on their galaxies »

Jarle Brinchmann
Sterrewacht Leiden (Leiden, Pays-Bas)

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. Their progenitors are very massive stars with substantial wind-loss and the mere detection of these stars in a range of environments can therefore help constrain models for the evolution of massive stars. Their luminosity make them detectable at large distances even in the integrated spectra of galaxies, these are sometimes known as Wolf-Rayet galaxies.
Here we discuss the detection of these features in galaxies from z~2 where Wolf-Rayet features are seen in co-added Lyman Break Galaxy spectra and in local Universe where we have carried out a search for WR galaxies in the Sloan Digital Sky Survey. In the latter survey we were able to more than double the number of such galaxies found with a total of 570 secure and 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 close with a discussion of the low- and high-redshift results and what this is teaching us about the properties of massive stars and possible implications for models of the evolution of massive stars.
vendredi 10 octobre 2008 - 11:00
Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris
Page web du séminaire / Seminar's webpage