The contribution of HI-rich galaxies to the damped Lyα absorber population at z=0

We present a study of the expected properties of the low-redshift damped Lyalpha absorber population determined from a sample of H I selected galaxies in the local universe. Because of a tight correlation between the H I mass and H I cross section, which we demonstrate spans all galaxy types, we can use our H I selected sample to predict the properties of the absorption-line systems. We use measurements of the number density and H I cross section of galaxies to show that the total H I cross section at column densities sufficient to produce damped Lyalpha absorption is consistent with no evolution of the absorber population. We also find that the dN/dz distribution is dominated by galaxies with H I masses near 10(9) M(circle dot). However, because of the large dispersion in the correlation between H I mass and stellar luminosity, we find that the distribution of dN/dz as a function of L(J) is fairly flat. In addition, we examine the line widths of the H I-selected galaxies and show that there may be evolution in the kinematics of H I-rich galaxies, but it is not necessary for the higher redshift population to contain a greater proportion of high-mass galaxies than we find locally.