Résumé / Abstract Seminaire_IAP
« Where do QSO absorption lines come from ? »

Donald G. York
Univ. Chicago (Chicago, Illinois, Etats-Unis d'Amérique)

The analysis of spectra of QSOs (Quasi-Stellar Objects, or quasars) from the archive of the Sloan Digital Sky Survey is being used to answer long-standing questions of where the absorbers in QSO spectra come from. Some systems must arise in intervening galaxies, though several tests of this simplest hypothesis have failed in the last few years: some may come from L* galaxies, several from dwarf galaxies, but some are unexplained by the hypothesis. A confounding result is the discovery that absorbers with 19 < Log N(HI) < 20.3 have average abundances that are solar and show evidence of dust depletion (but no 2175 Å bump), in contrast with the sub-solar and dust free gas in the systems with higher values of N(HI). Those systems within 3000 km/sec are, in part, from the host galaxy of the QSO and new results on the association will be presented: ionization trends with apparent ejection velocity have been detected. Some of these also come from clustering of galaxies around the QSO host galaxy. A long suspected population of absorbers ejected at velocities higher than 3000 km/sec has now been confirmed and is possibly related to the BAL population. Of order one-half of the CIV systems within 12,000 km/sec of the QSO are of this type and the ejected material comes from radio loud and radio quiet QSOs.
vendredi 4 avril 2008 - 11:00
Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris
Page web du séminaire / Seminar's webpage