  We present Keck LRIS spectroscopy along with NICMOS F110W (~J) and F160W (~H)
images of the galaxy HDF4-473.0 (hereafter 4-473) in the Hubble Deep Field,
with a detection of an emission line consistent with Ly-alpha at a redshift of
z=5.60. Attention to this object as a high redshift galaxy was first drawn by
Lanzetta, Yahil and Fernandez-Soto and appeared in their initial list of
galaxies with redshifts estimated from the WFPC2 HDF photometry. It was
selected by us for spectroscopic observation, along with others in the Hubble
Deep Field, on the basis of the NICMOS F110W and F160W and WFPC2 photometry.
For H_0 = 65 and q_0 = 0.125, use of simple evolutionary models along with the
F814W (~I), F110W, and F160W magnitudes allow us to estimate the star formation
rate (~13 M(solar)/yr). The colors suggest a reddening of E(B-V) ~ 0.06. The
measured flux in the Ly-alpha line is approximately 1.0*10^(-17) ergs/cm/s and
the restframe equivalent width, correcting for the absorption caused by
intervening HI, is approximately 90AA. The galaxy is compact and regular, but
resolved, with an observed FWHM of ~0.44". Simple evolutionary models can
accurately reproduce the colors and these models predict the Ly-alpha flux to
within a factor of 2. Using this object as a template shifted to higher
redshifts, we calculate the magnitudes through the F814W and two NICMOS
passbands for galaxies at redshifts 6 < z < 10.
