Journal Article

The relation between Lyman α absorbers and gas-rich galaxies in the local Universe

Marco Pierleoni, Enzo Branchini and Matteo Viel

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 388, issue 1, pages 282-292
Published in print July 2008 | ISSN: 0035-8711
Published online July 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13384.x
The relation between Lyman α absorbers and gas-rich galaxies in the local Universe

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We use high-resolution hydrodynamical simulations to investigate the spatial correlation between weak (NH i < 1015cm−2) Lyα absorbers and gas-rich galaxies in the local Universe. We confirm that Lyα absorbers are preferentially expected near gas-rich galaxies and that the degree of correlation increases with the column density of the absorber. The real-space galaxy auto-correlation is stronger than the cross-correlation (correlation lengths r0,gg= 3.1 ± 0.1 Mpc h−1 and r0,ag= 1.4 ± 0.1 Mpc h−1, respectively), in contrast with the recent results of Ryan-Weber, and the auto-correlation of absorbers is very weak. These results are robust to the presence of strong galactic winds in the hydrodynamical simulations. In redshift space, a further mismatch arises since at small separations the distortion pattern of the simulated galaxy–absorber cross-correlation function is different from the one measured by Ryan-Weber. However, when sampling the intergalactic medium along a limited number of lines-of-sight, as in the real data, uncertainties in the cross-correlation estimates are large enough to account for these discrepancies. Our analysis suggests that the statistical significance of difference between the cross-correlation and auto-correlation signal in current data sets is ∼1σ only.

Keywords: intergalactic medium; quasars: absorption lines; galaxies: statistics; large-scale structure of Universe

Journal Article.  7968 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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