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Paper: Gravitational Lensing by Damped LY alpha Absorbers
Volume: 156, Highly Redshifted Radio Lines
Page: 147
Authors: Smette, A.; Claeskens, J.-F.; Surdej, J.
Abstract: Spiral galaxies are thought to be the main responsible for the damped Ly-alpha (DLA) systems seen in QSO spectra. They can also act as gravitational lenses, affecting quantities derived in DLA surveys. Assuming that z > 0 spiral galaxies are similar to local ones, we find that, at z 0.5, the number density of DLA systems may be over-estimated by up to 90% and the HI cosmological density (OmegaHI) by up to 170% in a survey using bright bq = 16, zq ga 2 QSOs and in the absence of important extinction by dust. Applying our model to existing surveys, we find that OmegaHI is significantly over-estimated only in the z < 1.7 ones (by 34%). Furthermore, statistical tests indicate that these surveys are indeed affected by gravitational lensing at a 2.3% confidence level. If luminosity functions for flat-spectrum radio-sources and optically selected QSOs are similar in shape and slopes, similar Gling effects should affect surveys for 21cm absorbers using bright, high-z flat-spectrum radio-sources.
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