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Title: HST-COS observations of AGNs. II. Extended survey of ultraviolet composite spectra from 159 active galactic nuclei

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 {sub AGN} < 1.476 and construct a composite spectrum from 475 to 1875 Å. We identify the underlying AGN continuum and strong extreme ultraviolet (EUV) emission lines from ions of oxygen, neon, and nitrogen after masking out absorption lines from the H I Lyα forest, 7 Lyman-limit systems (N{sub H} {sub I}≥10{sup 17.2} cm{sup –2}) and 214 partial Lyman-limit systems (14.5
Authors:
 [1] ;  [2] ; ;  [3]
  1. Present address: Astronomy Department, University of Texas, Austin, TX 78712, USA. (United States)
  2. Also at Institute of Astronomy, Cambridge University, Cambridge CB3 OHA, UK. (United Kingdom)
  3. CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)
Publication Date:
OSTI Identifier:
22370473
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 794; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ACCRETION DISKS; DATA; EMISSION; EXTREME ULTRAVIOLET RADIATION; FAR ULTRAVIOLET RADIATION; GALAXIES; GALAXY NUCLEI; HEATING; IONS; LUMINOSITY; MASS; NEON; NITROGEN; OXYGEN; QUASARS; RED SHIFT; SPACE; SPECTRA; TELESCOPES