L-GAMMA-ALPHA ABSORPTION-LINE SYSTEMS IN THE GRAVITATIONAL LENS Q0957+561

Far-ultraviolet spectra of the gravitational lens components Q0957+561 A and B were obtained with the Hubble Space Telescope Faint Object Spe ctrograph (HST FOS). Two previously known absorption-line systems were detected at redshifts z(damped) = 1.3911 and z(Ly alpha) = 1.1249. Th eir prominent absorption features are superposed on intense QSO contin uum emission between lambda lambda 900-1400 in the quasar rest frame. Strong O VI lambda 1033, Ly alpha lambda 1216, and N V lambda 1240 lin e emission found at the QSO redshift (Z(QSO) = 1.41) accompany the abs orption-line systems. Ly alpha through Ly epsilon associated with the damped absorption system were found in both lensed components, togethe r with other ionic species of N I, N III, C II, C III, Si II, Si III, and O I. We tentatively identify O VI lambda lambda 1033, 1037 absorpt ion at the damped Ly alpha redshift, which, if confirmed, would be the highest ionization species yet detected in such systems. The equivale nt widths of the Lyman series in Q0957+561A are measurably greater com pared with absorption in 0957+561B, consistent with the narrower and s hallower depth of the Lyman series line profiles in image B. The diffe rences of the damped Lyman series absorption in the lensed components are the only significant spectral characteristic that distinguishes th e far-ultraviolet spectra of 0957+561A and B. These results indicate t hat the damped Ly alpha absorber is inhomogeneous over scale lengths o f similar to 200 pc, which corresponds to the beam separation at the d amped Ly alpha redshift. However, the equivalent widths of neutral and ionized metals in lens components A and B are correlated, which sugge sts these spectral features arise in an extended region. The metal lin e-absorption strength is consistent with lower column densities compar ed with the hydrogen line-forming region. Thus, the small coherence le ngth scale indicated by the difference in hydrogen line absorption bet ween the lensed components suggests the geometric ray paths intercept different regions of a galactic disk that is viewed pole-on, while the metal absorption occurs in the halo.