The circum-galactic medium of quasars: CIV absorption systems

Abstract: We investigate the properties of the circumgalactic gas in the halo of quasar host galaxies from CIV absorption line systems. Optical spectroscopy of closely aligned pairs of quasars (projected distance \leq 200 kpc) obtained at the Gran Telescopio Canarias is used to investigate the distribution of the absorbing gas for a sample of 18 quasars at z \sim 2. We found that the detected absorption systems of EW \geq 0.3Ang associated with the foreground QSO are revealed up to 200 kpc from the center of the host galaxy. The structure of the absorbing gas is rather patchy with a covering fraction of the gas that quickly decreases beyond 100 kpc. These results are in qualitative agreement with those found for the lower ionisation metal Mg II 2800 Ang.