NEAR-INFRARED OBSERVATIONS OF A REDSHIFT-4.92 GALAXY - EVIDENCE FOR SIGNIFICANT DUST ABSORPTION

Near-infrared imaging and spectroscopy have been obtained of the gravi tationally lensed galaxy at z = 4.92 discovered in Hubble Space Telesc ope (HST) images by Franx et al. Images at 1.2, 1.6, and 2.2 mu m show the same are morphology as the HST images. The spectrum with resoluti on lambda/Delta lambda similar to 70 shows no emission lines with equi valent width stronger than 100 Angstrom in the rest-frame wavelength,r ange 0.34-0.40 mu m. In particular, [O II] lambda 3727 and [Ne III] la mbda 3869 are not seen. The energy distribution is quite blue, as expe cted for a young stellar population with the observed Ly alpha flux. T he spectral energy distribution can be fitted satisfactorily for such a young stellar population when absorption by dust is included. The mo dels imply a reddening 0.1 mag < E(B - V) < 0.4 mag. The stellar mass of the lensed galaxy lies in the range of 2-16 x 10(9) M-circle dot. T his is significantly higher than estimates based on the HST data alone . Our data imply that absorption by dust is important to redshifts of similar to 5.