Résumé / Abstract Seminaire_IAP
« IGM metallicity: wide spread and cosmic evolution »

Jacqueline Bergeron

At z~2-3, a severe problem of missing metals was already recognized at the beginning of the VLT era and is still unsolved. Census of produced metals compared to those observed revealed an order of magnitude shortfall of detected metals. It was then suggested that the missing metals could reside in a hot phase of the intergalactic medium (IGM). I will briefly review the two methods used to derive IGM abundances based on QSO absorption line surveys, statistical analysis of pixel optical depths and studies of individual systems. Abundances derived for CIV and OVI samples drawn from the ESO VLT-UVES Large Programme will be given. A striking result is the bimodal distribution of [O/H] with median values close to 0.01 and 0.5 solar. This underlines the limitation in interpreting the IGM abundances inferred from statistical analyses of IGM regions with low N(HI), i.e. gas densities close to the mean cosmic baryon density. The metal-rich population should trace active sites of star formation, and could be linked to galactic winds as suggested by simulations. Altough the metal cosmic density is larger by a factor of ~2 than previously estimated, there is still a problem of missing metals. X-ray spectroscopy with future satellites may provide the answer. I will present the potentialities of future ELTs for probing metal enrichment in the low density IGM at z~3 and understanding the early chemical evolution of the Universe at z~7-15. For the latter, there is a complementary with SKA. I will outline the ELTs requirements due to the foreseen faintness of the early generations of galaxies, QSOs and transient objects.
vendredi 14 avril 2006 - 11:00
Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris
Page web du séminaire / Seminar's webpage