The ionizing fluxes from quasars and other active galactic nuclei (AGNs) are critical for interpreting their emission-line spectra and for photoionizing and heating the intergalactic medium. Using far-ultraviolet (FUV) spectra from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), we directly measure the rest-frame ionizing continua and emission lines for 159 AGNs at redshifts 0.001<z_AGN_=10^17.2^/cm2) and 214 partial Lyman-limit systems (14.5<logN_HI_<17.2). The 159 AGNs exhibit a wide range of FUV/EUV spectral shapes, F_v_{propto}{nu}^{alpha}{nu}^, typically with -2<={alpha}{nu}<=0 and no discernible continuum edges at 912 {AA} (H I) or 504 {AA} (He I). The composite rest-frame continuum shows a gradual break at {lambda}br{approx} 1000 {AA}, with mean spectral index {alpha}{nu}=-0.83+/-0.09 in the FUV (1200-2000 {AA}) steepening to {alpha}{nu}=-1.41+/-0.15 in the EUV (500-1000 {AA}). We discuss the implications of the UV flux turnovers and lack of continuum edges for the structure of accretion disks, AGN mass inflow rates, and luminosities relative to Eddington values.
Cone search capability for table J/ApJ/794/75/table1 (COS Observations (159 AGN Targets Ordered by Redshift))
