Multiple QSO images with arcminute splittings

摘要: 1. The methodology just described is adequate to rule out the gravitational lens hypothesis if narrow forbidden lines are detected with different properties, allowing accurate redshift determinations, or MgII emission show a significant shift between pair of sight. 2. When no line observed, and low ionization have similar properties (redshifts, profiles), issue logically difficult, since spectral differences likely be observed due systematic trend for high broad shifted respect (Gaskell 1982, Wilkes 1984). Q1146+111 B C images good example (Turner et al. 1986, Turner 1986). For such ambiguous cases, band deep CCD exposures few arcminute square field around multiple QSO may supplement efficiently spectroscopic studies nuclei, by searching candidate cluster galaxies associated QSOs. 3. In addition these observations, there growing evidence that clustering occur over wide range angular separations (Bahcall Djorgovski 1987). Further observations on this phenomenon should provide clues formation large scale structures at redshift.