1998AJ....116.2617S

We present spectrograms of the faint V-drop (V₆₀₆ = 28.1, I₈₁₄ = 25.6) galaxy pair HDF 3-951.1 and HDF 3-951.2 obtained at the Keck II Telescope. In a recent study, Fernández-Soto, Lanzetta, & Yahil derive a photometric redshift of z_ph=5.28^+0.34_–0.41 (2 σ) for these galaxies; our integrated spectrograms show a large and abrupt discontinuity near 7710±5 Å. This break is almost certainly due to the Lyα forest because its amplitude 1-f^short_ν/f^long_ν>0.87, 95% confidence limit) exceeds any discontinuities observed in stellar or galactic rest-frame optical spectra. The resulting absorption break redshift is z = 5.34±0.01. Optical/near-IR photometry from the HDF yields an exceptionally red (V₆₀₆ - I₈₁₄) color, consistent with this large break. A more accurate measure of the continuum depression blueward of Lyα utilizing the imaging photometry yields D_A = 0.88.

The system as a whole is slightly brighter than L^*₁₅₀₀ relative to the z ∼ 3 Lyman break population, and the total star formation rate inferred from the UV continuum is ~22 h^–2₅₀ M_☉.yr^–1 (q₀ = 0.5) assuming the absence of dust extinction. The two individual galaxies are quite small (size scales ≲1 h^–1₅₀ kpc). Thus these galaxies superficially resemble the ``building blocks'' of Pascarelle and coworkers; if they comprise a gravitationally bound system, the pair will likely merge in a timescale ∼100 Myr.