OBSERVATIONS OF QSO J2233-606 IN THE SOUTHERN HUBBLE DEEP FIELD

The Hubble Deep Field South (HDF-S) Hubble Space Telescope (HST) obser vations are expected to begin in 1998 October. We present a composite spectrum of the QSO in the HDF-S held covering UV/optical/near-IR wave lengths, obtained by combining data from the Australian National Unive rsity 2.3 m telescope with STIS on the HST.(1) This intermediate-resol ution spectrum covers the range 1600-10000 Angstrom and allows us to d erive some basic information on the intervening absorption systems whi ch will be important in planning future higher resolution studies of t his QSO. The QSO J2233 - 606 coordinates are alpha = 22(h)33(m)37(s).6 , delta = -60 degrees 33'29'' (J2000), the magnitude is B = 17.5, and its redshift is z(em) = 2.238, derived by simultaneously fitting sever al emission lines. The spectral index is alpha = -0.7 +/- 0.1, measure d between the Ly alpha and Mg II emission lines. Many absorption syste ms are present, including systems with metal lines redward of the Ly a lpha emission line at z(abs) 2.204, 1.942, 1.870, 1.787 and a few very strong Ly alpha features at z(abs) = 2.077, 1.928, without similarly strong metal lines. There is a conspicuous Lyman limit (LL) absorption system that is most likely associated with the z(abs) = 1.942 system with a neutral hydrogen column density of N-HI = (3.1 +/- 1.0) x 10(17 ) cm(-2). There is some evidence for the presence of a second LL absor ber just to the blue of the conspicuous system at z = 1.870. We have e mployed a new technique, based on an analysis of the shape of the obse rved spectrum in the region of the LL absorption, to explore the prope rties of the gas. We tentatively conclude that this system might have suitable characteristics for measuring the deuterium-to-hydrogen (D/H) ratio.