SPECTRAL DIFFERENCES IN THE QSO PAIRS Q1634+267A,B AND Q2345+007A,B AND THE GRAVITATIONAL LENS INTERPRETATION

We present new high signal-to-noise ratio, moderate dispersion spectra over the wavelength range 3150-7000 angstrom of two of the widest separation, unconfirmed gravitational lens candidates, Q1634 + 267 A,B (separation = 3.77") and Q2345 + 007A,B (separation = 7.03"). Aside from the obvious interest in establishing whether or not these pairs are gravitionally lensed images, both of these pairs are capable of setting extremely interesting limits on the sizes of intervening Lyman alpha and heavy-element absorption systems. For Q1634 + 267A,B, the detailed line profile and continuum shapes strongly support the gravitational lensing hypothesis; however, we find that the Ly alpha, N V, C IV, Si IV emission lines of the two images exhibit as much as a 1000 km s-1 relative shift in velocity, whereas the C III] and Mg II lines are consistent with no velocity shift, as found by previous workers. While the emission line profiles and redshifts of Q2345 + 007A and B are remarkably similar (DELTA-upsilon-B-A = 15 +/- 20 km s-1), the line-to-continuum ratios for various lines differ markedly; the intensity ratios for C IV, Si IV, and Mg II appear to scale roughly with the continuum ratio of the two spectra, whereas the Lyman alpha and especially C III] intensity ratios differ significantly from the observed continuum ratio. We conclude that both of the pairs in question are gravitationally lensed; however, the peculiarities of the emission line properties are puzzling, and may be providing information on the structure of QSO broad line regions. We discuss several possible origins for the differing emission line spectra under the gravitational lensing hypothesis. We favor the notion that there must be large temporal variations, occurring on timescales of about a year or less, in the relative redshifts (and strengths) of emission lines formed in different parts of the QSO emitting regions; we predict that such variations will be found if the spectra of single QSOs are monitored. For Q2345 + 007A,B, we report the discovery of at least three, and possibly four, new heavy element absorption systems in the spectra. Thus, several of the lines which have been assumed to be "Lyman alpha forest" lines are probably associated with heavy element systems. Contamination of the "Lyman alpha forest" sample with heavy element lines may have significantly affected previous inferred limits on the sizes of the intergalactic clouds. A possible Mg II absorption system at z = 0.7545 in the spectrum of Q2345 + 007B may arise in material associated with a lens, and may have been detected as a resolved component of B in high resolution imaging studies of the pair. The possibility of using spectra of Q2345 + 007A,B to set useful limits on the characteristic sizes of, and structures within, the heavy-element absorbing regions is explored.