QSO heavy element absorption systems and the nature of the metagalactic ionizing flux at high redshift

Abstract

view Abstract Citations (60) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS QSO Heavy Element Absorption Systems and the Nature of the Metagalactic Ionizing Flux at High Redshift Steidel, Charles ; Sargent, Wallace L. W. Abstract Given that the observed QSOs cannot account for the intensity of the metagalactic ultraviolet flux at high redshift, the possible contribution from early-type stars in young or forming galaxies is examined. Based on the observed ionization state of heavy element absorption systems in the spectra of QSOs, and using photoionization models, arguments are presented which appear to rule out the possibility of early-type stars in young or forming galaxies are dominating the metagalactic ultraviolet flux up to a redshift of at least z ~ 4. Specifically, the stellar contribution cannot be more than comparable to the AGN contribution, and thus it appears that unaccounted-for sources of ionizing radiation which have spectral energy distributions similar to those of AGNs must be presented at high redshifts. Publication: The Astrophysical Journal Pub Date: August 1989 DOI: 10.1086/185504 Bibcode: 1989ApJ...343L..33S Keywords: Absorption Spectra; Computational Astrophysics; Lyman Alpha Radiation; Quasars; Red Shift; Ultraviolet Spectra; Active Galactic Nuclei; Astronomical Models; Heavy Elements; Photoionization; Spectral Energy Distribution; Astrophysics; COSMOLOGY; GALAXIES: INTERGALACTIC MEDIUM; QUASARS full text sources ADS |