Mathematics – Probability
Scientific paper
Oct 1983
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983apj...273..450n&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 273, Oct. 15, 1983, p. 450-457.
Mathematics
Probability
44
Abundance, Intergalactic Media, Lyman Alpha Radiation, Lyman Beta Radiation, Oxygen, Quasars, Absorption Spectra, Line Spectra, Radiation Spectra, Signal To Noise Ratios
Scientific paper
A composite spectrum of the Lyα-Lyβ clouds seen in absorption in the spectra of the quasars 4C 5.34 (0805+046) and OQ 172 (1442+101) has been synthesized from the data of Chen et al. and Peterson et al. to enhance the available signal-to-noise ratio and to investigate the question of the metal abundance of the clouds. Apart from Lyα and Lyβ, we find no evidence for species other than O VI in the line absorption of the composite spectrum. We are forced to conclude that the identification of O VI has a 96% probability of being real. Assuming that the clouds are photoionized by the background quasar flux given by Sargent et a!., we derive metal abundances (or limits) for C, N, and 0. If the clouds are confined by a hotter intergalactic medium as suggested by Sargent et a!., we find [C/H] ≤ - 1.1, [N/H] ≤ -0.8, and [O/H] = -1.9. The oxygen result is relatively insensitive to the form of the quasar background flux and is consistent with Population II abundances, rather than with the clouds having primeval (i.e., zero heavy element) abundances. We note that the result can be understood in terms of Oort's hypothesis that the Lyα-Lyβ clouds are the remnants of material which formed superclusters, if the clouds have been enriched by matter driven out by winds from the clusters of galaxies which comprise the superclusters.
The composite Lyα and Lyβ profiles of the redshift systems having rest equivalent widths W(Lyα) ≥ 1.0 Å are apparently inconsistent with the prediction of Fransson and Epstein that the Lyα lines should have double minima as the result of originating in material which has been driven from dwarf galaxies.
Hartwick David A. F.
Norris Jackson
Peterson Bruce A.
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