Comparing Galaxies and Lyman Alpha Absorbers at Low Redshift

Abstract

A scenario is explored in which Lyman alpha absorbers at low redshift arise from lines of sight through extended galaxy disks, including those of dwarf and low surface brightness galaxies. A population of galaxies is simulated based upon observed distributions of galaxy properties, and the gas disks are modeled using pressure and gravity confinement. Some parameter values are ruled out by comparing simulation results with the observed galaxy luminosity function, and constraints may be made on the absorbing cross sections of galaxies. Simulation results indicate that it is difficult to match absorbers with particular galaxies observationally since absorption typically occurs at high impact parameters (>200 kpc) from luminous galaxies. Low impact parameter absorption is dominated by low luminosity dwarfs. A large fraction of absorption lines is found to originate from low surface brightness galaxies, so that the absorbing galaxy is likely to be misidentified. Low redshift Lyman alpha absorber counts can easily be explained by moderately extended galaxy disks when low surface brightness galaxies are included, and it is easily possible to find a scenario which is consistent with observed the galaxy luminosity function, with low redshift Lyman limit absorber counts, and with standard nucleosynthesis predictions of the baryon density, Omega_Baryon.

17 pages, 8 figures, accepted to the Astrophysical Journal

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• A new HI catalog of Low Surface Brightness galaxies out to z=0.1 - Tripling the number of massive LSB galaxies Known
• A Study of Lyman-Alpha Quasar Absorbers in the Nearby Universe
• The Low Surface Brightness Extent of the Fornax Cluster
• The Local Lyman-Alpha Forest: Absorbers in Galaxy Voids
• The association between gas and galaxies I: CFHT spectroscopy and pair analysis
• The Effects of Starburst Activity on Low Surface Brightness Disk Galaxies
• High Metallicity Mg II Absorbers in the z < 1 Lyman alpha Forest of PKS 0454+039: Giant LSB Galaxies?
• The HI Column Density Distribution Function at z=0: the Connection to Damped Ly alpha Statistics
• Galaxy Selection and Clustering and Lyman alpha Absorber Identification
• Low Redshift QSO Lyman alpha Absorption Line Systems Associated with Galaxies
• Galaxies as Fluctuations in the Ionizing Background Radiation at Low Redshift
• The HI Detection of Low Column Density Clouds and Galaxies
• Simulations of LyαAbsorption from Low Surface Brightness Galaxies