0 Assigned ID: 82 ----- Attempting Submission 1 (Wed Apr 09 00:41:16 GMT 2014) ----- HST Phase I Proposal 82 (EUV_slope_AR.apt) successfully submitted. ----- Attempting Submission 2 (Thu Apr 10 04:01:19 GMT 2014) ----- HST Phase I Proposal 82 (EUV_slope_AR.apt) successfully submitted. ----- Attempting Submission 3 (Fri Apr 11 07:18:29 GMT 2014) ----- Quasars are responsible for the majority of photoionization of the intergalactic medium over most of the history of the Universe, dominating especially at the higher energies that produce many astrophysically important ions. However, direct observations of their intrinsic ionizing spectra have thus far been largely limited to energies less than ~1.5 Ryd. We propose to directly measure the 2-3 Ryd spectral indices of about 40 z ~ 3 quasars (originally observed to study helium reionization), carefully accounting for all Galactic and intergalactic modifications of the spectrum, in order to construct for the first time an accurate picture of this large portion of the ionizing spectrum of quasars. Such a fully corrected measurement of the ionizing continuum at these energies has not been made before, and the available sample allows a robust determination. AGN/QUASARS Default Medium false true false false false SUPPORTED