Data & Survey Procedures

For our survey of associated systems, we chose a subsample of HST Quasar Absorption Line Key Project QSOs which had been observed at resolution R=1300~230 km/s (with either the G130H, G190H, or G270H gratings) and fell into the redshift range 0.2< z < 1.2 (so that the CIV emission line was covered). Using the same method as the Key Project [8], we performed a survey of associated systems - selected by CIV, NV, and OVI - with a detection threshold of 3-sigma, more sensitive than the 4.5-sigma threshold used by the Key Project. We found 15 QSO with associated systems selected by CIV while one additional QSO had an associated system selected by OVI. No additional systems were found selected by NV and only one of the CIV-selected systems was not found by the Key Project. Since truly intrinsic NALs are often variable, it is likely that some were not detected. Thus, the number of NALQSOs is at least 16/64=25% of the sample.