Discovery of BAL Structure in the Gravitational Lens Candidate UM 425

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Session 23 -- Gravitational Lensing
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

[23.02] Discovery of BAL Structure in the Gravitational Lens Candidate UM 425

R.J. Oliversen, S.P. Maran (NASA-GSFC)

The UV line profile structure found with the International Ultraviolet Explorer (IUE) in the brightest (Image A) of four multiple-images in the gravitational lens candidate UM 425 = Q1120+019 indicates pronounced Broad Absorption Line (BAL) structure in the high-ionization resonance lines of O VI 1033A and N V 1240A. The broad O VI absorption trough extends to velocities of ~12,000km/s, and contains velocity structure similar to that found in the absorption troughs of C IV 1550A in BAL QSO's. We obtained a quasar redshift of z = 1.471 from the Lyman-alpha 1216A emission centroid, consistent with the redshift found by Meylan and Djorgovski (1988) from C III] 1909A and Mg II 2800A in the optical. A strong absorption feature in the blue wing of the QSO Lyman-alpha emission line may be a hydrogen absorption system at a z = 1.437, or it may be formed by the superposition of N V BAL absorption on the broad QSO Lyman-alpha emission profile. A Lyman-edge 912A absorption system was not observed in the QSO rest frame. The lack of BAL structure in other absorption lines found here, that includes N II(1) 1084A and S IV(1) 1063-1073A and C III 1175A, suggests they are unrelated to the BAL component. IUE SWP 1200-2000A spectra obtained of UM 425 indicate quasar continuum down to 1450A (observed rest frame) below which the flux is either absent or weak. The absorption edge at 1450A may correspond to the Lyman-edge 912A redshifted by z ~ 0.6, consistent with the galaxy and suspected rich cluster of galaxies which are believed to lens UM 425.

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