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

Journal Article · Tue Aug 01 00:00:00 EDT 1989 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/185504· OSTI ID:5343621

Steidel, C; Sargent, W L.W. ^[1]

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1. Palomar Observatory, Pasadena, CA (USA)

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 that early-type stars in young or forming galaxies are dominating the metagalactic ultraviolet flux up to a redshift of at least z about 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 present at high redshifts. 25 refs.

• OSTI ID: 5343621
• Journal Information: Astrophysical Journal; (USA), Vol. 343; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
IONIZING RADIATIONS
RADIATION SOURCES
QUASARS
ABSORPTION SPECTRA
ASTROPHYSICS
ELEMENTS
ENERGY SPECTRA
GALACTIC EVOLUTION
GALAXIES
GALAXY NUCLEI
LYMAN LINES
MATHEMATICAL MODELS
PHOTOIONIZATION
RED SHIFT
STARS
ULTRAVIOLET SPECTRA
COSMIC RADIO SOURCES
IONIZATION
RADIATIONS
SPECTRA
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources
640105 - Astrophysics & Cosmology- Galaxies