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Evidence for structure in the H I column density distribution of QSO absorbersThe H I column density distribution function of QSO absorption line systems is investigated using recent data with high spectral resolution, and extensive surveys of the Lyman limit systems and damped Ly-alpha systems. The hypothesis that the differential distribution function is fitted by a single power law is rejected at the 99 percent confidence level. A double power law, with a break at N(H I) = 10 exp 16/sq cm, also provides a poor fit over the range in which the sample is complete. While there are no discontinuities in the observed distribution, there is a clear flattening at N(H I) of about 10 exp 16/sq cm, compared to lower column densities. These observed features can be understood using models of photoionized clouds which are confined by an external pressure with density profiles governed by gravity. In particular, the flattening at N(H I) of about 10 exp 16/sq cm can be explained in terms of a transition between metal-poor and metal-rich systems.
Document ID
19930054531
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Petitjean, P.
(Cambridge Univ. Inst. of Astronomy, United Kingdom; CNRS, Inst. d'Astrophysique; Paris, Observatoire, Meudon, France)
Webb, J. K.
(New South Wales Univ. Kensington, Australia)
Rauch, M.
(Cambridge Univ. Inst. of Astronomy, United Kingdom; Carnegie Institution of Washington, Observatories, Pasadena, CA, United States)
Carswell, R. F.
(Cambridge Univ. Inst. of Astronomy, United Kingdom)
Lanzetta, K.
(California Univ. La Jolla, United States)
Date Acquired
August 16, 2013
Publication Date
May 15, 1993
Publication Information
Publication: Royal Astronomical Society, Monthly Notices
Volume: 262
Issue: 2
ISSN: 0035-8711
Subject Category
Astrophysics
Accession Number
93A38528
Funding Number(s)
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other

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