Extension of Lyman-alpha Complexes from HST Observations of Four Pairs of Quasars

Abstract

We present HST observations of four pairs of quasars with 2,3 arcmin angular separation and redshift z 0.9. We apply the Nearest-Neighbor method to the sample of observed Lyman-alpha lines with rest equivalent width greater than 0.3 Angstrum. According to Monte-Carlo simulations, we detect an excess of coincidences with velocity difference smaller than 500 km/s