The optical identification of a primeval galaxy at z>~4.4

We have obtained, with the SUSI CCD camera on the ESO 3.5-m NTT, deep images in the BVRI bands of the field centred on the QSO BR 1202-0725 (z_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 arcsec from the QSO, corresponding to 13h^-150 kpc at z~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, is discussed. We conclude that the 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 ~30 M_solar 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