Narrow associated quasi-stellar object absorbers: Clustering, outflows and the line-of-sight proximity effect

Abstract

Using data from the Sloan Digital Sky Survey data release 3 (SDSS DR3), we investigate how narrow (<700 km s-1)CIV and Mg II quasar absorption-line systems are distributed around quasars. The C IV absorbers lie in the redshift range 1.6 < z < 4 and the Mg II absorbers in the range 0.4 < z < 2.2. By correlating absorbers with quasars on different but neighbouring lines of sight, we measure the clustering of absorbers around quasars on comoving scales between 4 and 30 Mpc. The observed comoving correlation lengths are ro ~ 5h-1Mpc, similar to those observed for bright galaxies at these redshifts. Comparing correlations between absorbers and the quasars, in whose spectra they are identified, then implies: (i) that quasars destroy absorbers to comoving distances of ~300 kpc (C IV) and ~800 kpc (Mg II) along their lines of sight; (ii) that ≳40 per cent of C IV absorbers within 3000 km s-1 of the quasi-stellar object are not a result of large-scale clustering but rather are directly associated with the quasar itself; (iii) that this intrinsic absorber population extends to outflow velocities of the order of 12 000 km s-1; (iv) that this outflow component is present in both radio-loud and radio-quiet quasars and (v) that a small high-velocity outflow component is also observed in the Mg II population. We also find an indication that absorption systems within 3000 km s-1 are more abundant for radio-loud quasars than for radio-quiet quasars. This suggests either that radio- loud objects live in more massive haloes, or that their radio activity generates an additional low-velocity outflow, or both. © 2008 The Authors. Journal compilation © 2008 RAS.