We present Keck LRIS spectroscopy along with NICMOS F110W ( \sim J ) and F160W ( \sim H ) images of the galaxy HDF 4–473.0 ( 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 km s ^ { -1 } Mpc ^ { -1 } and q _ { 0 } = 0.125 , use of simple evolutionary models along with the F814W ( \sim I ) , F110W , and F160W magnitudes allow us to estimate the star formation rate ( \sim 13 M _ { \odot } / yr ) .
The colors suggest a reddening of E ( B-V ) \sim 0.06 .
The measured flux in the Ly- \alpha line is approximately 1.0 ~ { } \times 10 ^ { -17 } ergs cm ^ { -2 } s ^ { -1 } and the restframe equivalent width , correcting for the absorption caused by intervening H I , is approximately 90 Å .
The galaxy is compact and regular , but resolved , with an observed FWHM of \sim 0.44 ^ { \prime \prime } .
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 .