Statistics Martin A. Zwaan , Marc A. W. Verheijen , Frank H. Briggs, PASA, 16 (1), 100
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The Há I Column Density Distribution Function at z=0: the Connection to Damped Ly
Statistics
Martin A. Zwaan 1 - Marc A. W. Verheijen 2
Frank H. Briggs 1
1 Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen, The Netherlands
zwaan, fbriggs@astro.rug.nl
2 National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801, U.S.A.
mverheij@aoc.nrao.edu
Abstract:
] at the present epoch for column densities
. These high column densities compare to those measured in damped Ly lines seen in absorption against background quasars. Although observationally rare, it appears that the bulk of the neutral gas in the Universe is associated with these damped Ly systems. In order to obtain a good anchor point at z=0 we determine in the local Universe by using 21cm synthesis observations of a complete sample of spiral galaxies. We show that for damped Ly systems has changed significantly from high z to the present and that change is greatest for the highest column densities. The measurements indicate that low surface brightness galaxies make a minor contribution to the cross section for Há I, especially for
.
Keywords: galaxies: ISM -- galaxies: evolution -- quasars: absorption lines
- Introduction
- How to determine at z=0?
- The Ursa Major Cluster
- The Column Density Distribution Function
- Contribution of Low Surface Brightness Galaxies
- Conclusions and Discussion
- References
á© Copyright Astronomical Society of Australia 1997