Friday, January 18, 2002, 16:00
WHGA Auditorium
Prof. P. Petitjean, IAP Paris
Abstract:
Absorption lines observed in the spectra of remote (high-redshift)
quasars reveal gas located anywhere on the line of sight between us
and the quasar. Any intervening object, as tenuous as a diffuse
intergalactic cloud or as dense as a galactic disk, located by
chance in front of the quasar, produces a recognizable absorption
in the spectrum of the quasar. It is therefore possible to study
the physical characteristics of the intergalactic medium (density,
temperature, ionization-state, chemical composition) and their
cosmological evolution.
A coherent picture has emerged recently from the comparison of observations with the outputs of large-scale N-body numerical simulations in which the diffuse intergalactic gas traces the filamentary structures of the dark-matter. Most of the baryons at high redshift are in this diffuse gas which is therefore the reservoir for galaxy formation. One of the most interesting project for the next few years in this field is therefore to reconstruct the 3D spatial distribution of the gas and its connection to galaxies.