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Influence of Gravitational Lensing on Estimates of Ω in Neutral Hydrogen

Published online by Cambridge University Press:  25 May 2016

Matthias Bartelmann  and
Abraham Loeb
Matthias Bartelmann
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA Max-Planck-Institut für Astrophysik, Postfach 1523, 85740 Garching, Germany
Abraham Loeb
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

Extract

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A wealth of observational data supports the commonly held view that damped Lyman-α (Lyα) absorption in QSO spectra is associated with neutral-hydrogen (HI) disks in spiral galaxies. Most of the HI probed by QSO absorption lines is traced by damped Lyα lines because of their high column densities, N > 1020 cm–2. The spiral galaxies hosting the HI disks can act as gravitational lenses on the QSOs. If the HI column density increases towards the center of the disks, as suggested by observations of local galaxies, the magnification bias preferentially selects for high column-density systems. The estimates of HI in damped Lyα systems can then systematically be distorted by gravitational lensing.

Type
Chapter 4: Quasar Absorption Lines
Information
Symposium - International Astronomical Union , Volume 173: Astrophysical Applications of Gravitational Lensing , 1996 , pp. 97 - 98
Copyright
Copyright © Kluwer 1996 

References

Bartelmann, M., & Loeb, A., 1995, ApJ, submitted Google Scholar