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Title:
The Gunn-Peterson effect in the spectrum of the Z = 4.7 QSO 1202-0725: The intergalactic medium at very high redshifts
Authors:
Giallongo, E.; D'Odorico, S.; Fontana, A.; McMahon, R. G.; Savaglio, S.; Cristiani, S.; Molaro, P.; Trevese, D.
Affiliation:
AA(Osservatorio Astronomico di Roma, Monteporzio, Italy), AB(Osservatorio Astronomico di Roma, Monteporzio, Italy), AC(Università di Roma, Roma, Italy), AD(Università di Roma, Roma, Italy), AE(Università della Calabria, Cosenza, Italy), AF(Università della Calabria, Cosenza, Italy), AG(Osservatorio Astronomico di Trieste, Trieste, Italy), AH(Osservatorio Astronomico di Trieste, Trieste, Italy)
Publication:
Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 425, no. 1, p. L1-L4 (ApJL Homepage)
Publication Date:
04/1994
Category:
Astronomy
Origin:
STI
NASA/STI Keywords:
Absorption Spectra, Cosmology, Intergalactic Media, Line Spectra, Lyman Spectra, Quasars, Red Shift, Spectral Emission, Universe, Astronomical Models, Baryons, Nuclear Fusion, Optical Thickness, Ultraviolet Radiation
DOI:
10.1086/187296
Bibliographic Code:
1994ApJ...425L...1G

Abstract

A measure of the average depression between Lyman absorption lines in the spectrum of the faint quasar BR 1202-0725 (zem = 4.695) is presented. The relatively high resolution of the spectrum (approximately 40 km/s) allows the selection of regions free of strong absorption lines in the Lyman alpha forest. A reliable evaluation of the continuum shape is based on the careful flux calibration and on the large wavelength interval covered (5000-9300 A). A best estimate of tauGP is less than or equal to 0.02 +/- 0.03 has been found for the Gunn-Peterson optical depth at the highest absorption redshift observed at this resolution, z is approximately equal to 4.3. The derived baryon density of the intergalactic medium is OmegaIGM is approximately less than 0.01 if the observed quasars are the major contributor to the ionizing UV background flux. This limit, when compared with the total baryon density deduced from the nucleosynthesis, could imply that most of the baryons are already in bound systems at z approximately 5.

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