Abstract
The distribution of the absorption lines in the Lα forest of QSOs is re-examined in relation to both absorption and emission redshifts by analyzing a sample consisting of 20 QSO Lα forests.
On the one hand, the γ-value in the relationN(z abs)=N 0(1+z abs)γ is re-estimated by applying the maximum likelihood (ML) method to all the Lα forests in our sample as a whole as well as to the forests for individual QSOs. The global γ estimated is 2.20±0.28 and both the quasars with highest and lowestz em do not individually have a significant effect on it. A non-parametric test on the estimate of γ from individual QSOs shows that there is no significant difference between the numbers of positive and negative γ-values. This does not, therefore, favour the idea that for individual QSOsN(z abs) decreases with increasingz abs.
On the other hand, the possible correlation between the absorption line density and the emission redshift of the QSO itself, which was found by Bianet al. (1986, 1988) and re-discovered independently by Tytler (1987), is shown once again not only by the largerz em QSOs having larger mean density, but more importantly, at a rather high confidence level, by the fact that, at the same values ofz abs, QSOs with largerz em possess a greater number of Lα absorption lines.
A discussion of the ‘inverse effect’ suggests that it is still hard to say whether this effect really exists.
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Yulin, B. A new examination of absorption line density in the Lα forest of QSOs. Astrophys Space Sci 180, 113–131 (1991). https://doi.org/10.1007/BF00644233
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DOI: https://doi.org/10.1007/BF00644233