The Optical Identification of a Primeval Galaxy at z >~ 4.4

We have obtained with the SUSI CCD camera on the ESO 3.5m NTT deep images in the BVRI bands of the field centered on the QSO BRI 1202-0725 ($z_{\it em}=4.694$). In the final combined frames the stellar images have FWHM of 1,1,0.6 and 0.65 arcsec respectively. The R and I images show clearly a galaxy ${2.2}^{\mathrm{\prime }\mathrm{\prime }}$ from the QSO, corresponding to $13h_{50}^{-1}$ kpc at $z\sim 4.5$. Possible identification with the metal absorption systems seen in the line of sight to the QSO, including the highest redshift damped system known to date at $z=4.383$, are discussed. We conclude that its colours can be reconciled only with the spectrum of a primeval galaxy at z >~ 4.4, making it the most distant galaxy detected so far. From its magnitudes and models of young galaxy evolution we deduce that it is forming stars at a rate $\sim 30M_{\odot }$ yr${}^{-1}$ and has an estimated age of the order of ${10}^8$ yr or less, implying that the bulk of the stellar population formed at $z<6$.