Keck Spectroscopy of Objects with Lens-like Morphologies in the Hubble Deep Field

We present spectroscopy from the Keck telescope of three sets of objects inthe Hubble Deep Field which have lens-like morphologies. In the case ofJ123641+621204, which is composed of four objects with similar colors and amean separation of <= 0.8", we find at least two distinct components atredshifts of z=3.209 and z=3.220 which are separated by 0.5" spatially. Each ofthese components has narrow Ly-alpha emission, and possibly NV emission andSiIV and CIV in absorption or with a P-Cygni profile. The second case isJ123652+621227, which has an arc-like feature offset by 1.8" to the southwestof a red elliptical-like galaxy, and a ``counterimage'' offset 1.4" on theopposite side. We tentatively find a single line at 5301 AA at the spatialposition of the counterimage, and no corresponding emission line at theposition of the arc. The colors of the counterimage are consistent with theidentification of this line as Ly-alpha at z=3.36. The colors of the arc aredifferent than those of the counterimage, and thus both the colors and spectraindicate that this object is unlikely to be a gravitational lens. For a thirdlensing candidate (J123656+621221), which is a blue arc offset by 0.9" from ared, elliptical-like galaxy, our spectroscopy does not clearly resolve thesystem spatially, complicating the interpretation of the spectrum. We discusspossible identifications of features in the spectrum, and find thatgravitational lensing remains a possibility in this case. We conclude that thefrequency of strong gravitational lensing by galaxies in the HDF appears to bevery low. This result is difficult to reconcile with the introduction of acosmological constant to account for the large number of faint blue galaxiesvia a large volume element at high redshift.