Faint Object Spectrograph Observations of the Large-Redshift Gravitational Lens Candidate 1208+1011

Abstract

We report HST spectroscopic observations of the z = 3.8 gravitational lens candidate 1208+1011. Low-dispersion (R = 200) Faint Object Spectrograph data, covering the wavelength range 3700-7800 A, were obtained for each of the two components (V ~18.3 and 19.8 mag) and for a comparison (blank) field; the fainter component and the blank field are both separated by 0.47" from the brighter image. The spectra of both components possess strong Lyα/N V and O VI/Lyβ emission lines at a redshift of 3.8 as well as a number of similar absorption features. Both components have a ratio of the equivalent widths of the O VI complex to the Lyα complex much larger than the typical value seen in large-redshift quasars. There are small differences in the measured profiles of the Lyα and O VI/Lyβ emission lines of the images. These differences could be caused by absorption along different paths to a single lensed object, by unequal imaging of extended emissions, by systematic measuring errors, or by intrinsic differences in two nearly identical neighboring quasars.