Estimate of the Number of Intrinsic Systems

To estimate the fraction of associated systems which are intrinsic, we compute the number of intervening systems that we expect in the same redshift path. Jannuzi et al. (1998) find 107 CIV systems, detected at 4.5-sigma confidence, in a redshift path of dz=44. This implies a dN(CIV)/dz~107/44=2.43. The redshift path of this survey, since we only search a 10,000 km/s range about the peak, is dz = 64*10,000/300,000 = 2.13. We therefore expect to detect 2.43*2.13=5.2 CIV systems at 4.5-sigma confidence. Since we detect 15 at this sensitivity, about 66% of our systems are intrinsic.