1994A&A...287..719M

We present spectra of three intrinsically faint (M_V>-27) quasars: Q 0009-016 (z_em=1.997), Q 0347-241 (z_em=1.881) and Q 2116-358 (z_em=2.341). A total of 6 CIV absorption systems are detected, half of which are z_abs≃z_em systems occurring within {DELTA}v=±5000 km/s of the emission redshift. This high occurrence of z_abs≃z_em absorption is consistent with the existence of a statistical excess of CIV absorption systems near the quasar redshift, and with the hypothesis that such systems tend to occur in objects intrinsically fainter than M_V≃-27. In Q 0347-241, a new example of a z_abs>z_em system is found, having an apparent relative velocity of {DELTA}v≃-900 km/s with respect to the background quasar. The lack of NV absorption seen in this high-ionisation system suggests that the absorbing gas is under-abundant in nitrogen with respect to carbon by a factor of 10-100. Q 2116-358 exhibits two close z_abs ≃z_em systems at relative velocities {DELTA}v≃+3100 km/s and {DELTA} v≃+2000km/s. The ionisation levels of these two systems are markedly different, and correspond to a factor ≃20 difference in ionisation parameter. Moreover, the two systems are `inverted' in the sense that the lower ionisation system is the one closest to Q 2116-358 in velocity. A damped Lyα system with hydrogen column density of N_HI≃1.4x10²⁰cm^–2 is also detected in Q 2116-358 at z_abs=1.9966. An analysis of the observed line strengths indicates that the data are all consistent with heavy element abundances of 3% of solar values. Previous determinations of metalicities of intervening systems have all resulted in values of ≤20% of solar. In contrast, all three z_abs≃z_em systems have [C/H]>0, and we take this as evidence that z_abs≃z_em systems constitute a distinct class of absorbers of different nature than the intervening systems.