Near-Infrared Observations of a Redshift 5.34 Galaxy: Further Evidence for Dust Absorption in the Early Universe

Imaging at 1.25 and 2.20 μm has been obtained of the field containing the galaxy (RD1) found at redshift z =5.34 by Dey et al. This galaxy has been detected at 1.25 μm, while the lower redshift ( z =4.02) galaxy also found in the same field by Dey et al. was detected at both 1.25 and 2.20 μm. Comparison to stellar population synthesis models indicates that if RD1 is a young ( t <10 8 yr) galaxy, significant reddening ( A V >0.5 mag) is indicated. Combined with observations of other high-redshift systems, these data show that dust is likely to be an important component of young galaxies even at redshifts of z >5. The extinction-corrected monochromatic luminosity of RD1 at 1500 Å is then a factor of about 3 larger than L * 1500 as determined by Dickinson for z ~3 starburst galaxies. The implied star formation rate in RD1, corrected for extinction, is ~50-100 h −2 50 M ☉ yr -1 .