Three low-redshift quasars with absorption systems: IUE andoptical observations.

Abstract

The authors have discovered the first two cases of narrow absorption systems with an absorption redshift equal to the emission redshift (Δv ⪉ 500 km s^-1) in the low-redshift quasars PKS 1912-54 (z_em = 0.401) and PKS 2135-14 (z_em = 0.200). They also confirm the existence of a sharp absorption system (z_ab very low z_em) in the spectrum of PKS 2128-12 (z_em = 0.4996). The three quasars have been observed both in the far-UV and in the optical. A strong Lyman discontinuity is also present in PKS 1912-54. The absorption lines in PKS 2135-14 are found to vary, showing some resemblance to NGC 4151.