Detection of further UV-bright high-redshift QSOs

Abstract

We present successful UV observations with IUE of several newly discovered high-redshift QSOs from the Hamburg QSO Surveys. In addition to three previously discovered QSOs three new objects have been found to have lines of sight transparent to wavelengths as short as 1200 { Angstroms}: HS 0747+4259 (z = 1.9, V = 15.8); HS 1147+6556 (z = 2.21, V = 16.2); HE 2347-4342 (z = 2.89, V = 16.1). \tolerance 5000 We also report on the discovery of HE 0515-4414 which with z = 1.71 and V = 14.9 is the brightest known z > 1.5 QSO in the sky and among the most luminous objects in the universe. Our IUE long wavelength observations show HE 0515-4414 to be also the UV-brightest high-redshift QSO known (6 * 10(-15) erg cm(-2) { Angstroms}(-1) s(-1) ) with a damped Ly alpha system at z = 1.15. While HE 2347-4342 has been observed spectroscopically with HST (Reimers et al. \cite{rei97}), the other QSOs, in particular HE 0515-4414, are promising targets for HST and/or the Far Ultraviolet Spectroscopic Explorer (FUSE). Since the IUE mission has come to an end, we briefly discuss the outcome of the attempts to detect with IUE UV-bright high z QSOs. We show that the strategy that avoided QSOs with metal absorption systems and/or Lyman limit absorption already visible in low resolution optical spectra led to a detection rate at 1250 { Angstroms} of approximately 35 % (5 out of 14) for QSOs with Vla 16.5 and 2<= z<=3 using whole shift IUE exposures. Based on observations obtained at the VILSPA IUE Observatory of the European Space Agency, at the European Southern Observatory, La Silla, Chile, and at the German-Spanish Astronomical Center, Calar Alto, Spain