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Local galaxies as damped Lyman-$\alpha$ absorber analogues

Published online by Cambridge University Press:  06 October 2005

M. A. Zwaan
Affiliation:
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching b. München, Germany. email: [email protected]
J. M. van der Hulst
Affiliation:
Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
F. H. Briggs
Affiliation:
Research School for Astronomy & Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston, ACT 2611, Australia Australian National Telescope Facility, PO Box 76, Epping, NSW 1710, Australia
M. A. W. Verheijen
Affiliation:
Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
E. V. Ryan-Weber
Affiliation:
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB30HA, UK
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Abstract

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We calculate in detail the expected properties of low redshift DLAs under the assumption that they arise in the gaseous disks of galaxies like those in the $z\approx 0$ population. A sample of 355 nearby galaxies were analysed, for which high quality H I 21-cm emission line maps are available as part of an extensive survey with the Westerbork telescope (WHISP). We find that expected luminosities, impact parameters between quasars and DLA host galaxies, and metal abundances are in good agreement with the observed properties of DLAs and DLA galaxies. The measured redshift number density of $z=0$ gas above the DLA limit is $dN/dz=0.045\pm 0.006$, which compared to higher $z$ measurements implies that there is no evolution in the co-moving density of DLAs along a line of sight between $z\sim 1.5$ and $z=0$, and a decrease of only a factor of two from $z\sim 4$ to the present time. We conclude that the local galaxy population can explain all properties of low redshift DLAs.

Type
Contributed Papers
Copyright
© 2005 International Astronomical Union