Circumgalactic medium of quasars: C IV absorption systems

Abstract

We investigate the properties of circumgalactic gas in the halo of quasar (QSO) host galaxies from C IV absorption-line systems. We use the optical spectroscopy of closely aligned pairs of quasars (projected distance ≤ 200 kpc) obtained at the Gran Telescopio Canarias to investigate the distribution of the absorbing gas for a sample of 18 quasars at z ∼ 2. We have found that the detected absorption systems of EW ≥ 0.3 Å associated with the foreground QSOs are revealed up to 200 kpc from the centre of the host galaxy. The structure of the absorbing gas is 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 ionization metal Mg II λ2800 Å.