The intergalactic medium probed by quasar absorption lines

E. Rollinde, P. Petitjean
Institut d'Astrophysique de Paris, 98bis, boulevard Arago 75014 Paris, France

Observation of the intergalactic medium (IGM) through absorption spectra of quasars allows us to tackle many problems of physics and astrophysics. It provides new constraints in fundamental physics (expansion of the universe, variation of fundamental constants), but also in general cosmology (geometry of the Universe, growth of large scale structures) and on the reionization history of the Universe. More specifically, absorption spectra are also powerful probes of interactions between galaxies and the IGM through galactic winds and accretion of pristine gas. They reveal the interstellar medium in galaxies at high z through molecular lines. However, the uni-dimensional character of absorption spectra makes these studies complex and limited by many degeneracies that can be lifted by the combination of a large number of lines of sight. After describing the absorption spectra in general, I will review these different topics and the opportunities and challenges offered by this area of research.


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