Reconciling the local galaxy population with damped Lyman α cross-sections and metal abundances

By M. Zwaan, J. Hulst, Frank H. Briggs, Marc A. W. Verheijen, E. Ryan-Weber. 2005

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A comprehensive analysis of 355 high-quality Westerbork Synthesis Radio Telescope (WSRT) HI 21-cm line maps of nearby galaxies shows that the properties and incident rate of damped Lyman alpha absorption systems (DLAs) observed in the spectra of high-redshift QSOs are in good agreement with DLAs originating in gas discs of galaxies like those in the z approximate to 0 population. Comparison of low-z DLA statistics with the HI incidence rate and column density distribution f(N (HI)) for the local galaxy sample shows no evidence for evolution in the integral 'cross-section density' = l(-1) (l = mean free path between absorbers) below z approximate to 1.5, implying that there is no need for a hidden population of galaxies or H I clouds to contribute significantly to the DLA cross-section. Compared with z approximate to 4, our data indicate evolution of a factor of 2 in the comoving density along a line of sight. We find that dN/dz(z = 0) = 0.045 +/- 0.006. The idea that the local galaxy population can explain the DLAs is further strengthened by comparing the properties of DLAs and DLA galaxies with the expectations based on our analysis of local galaxies. The distribution of luminosities of DLA host galaxies, and of impact parameters between QSOs and the centres of DLA galaxies, is in good agreement with what is expected from local galaxies. Approximately 87 per cent of low-z DLA galaxies are expected to be fainter than L-*, and 37 per cent have impact parameters less than 1 arcsec at z = 0.5. The analysis shows that some host galaxies with very low impact parameters and low luminosities are expected to be missed in optical follow-up surveys. The well-known metallicity-luminosity relation in galaxies, in combination with metallicity gradients in galaxy discs, causes the expected median metallicity of low-z DLAs to be low (similar to 1/7 solar), which is also in good agreement with observations of low-z DLAs. We find that f(N H I) can be fitted satisfactorily with a gamma distribution, a single power law is not a good fit at the highest column densities N H I > 10(21) cm(-2). The vast majority (approximate to 81 per cent) of the H I gas in the local Universe resides in column densities above the classical DLA limit (N (H I) > 2 x 10(20) cm(-2)), with N (H I) similar to 10(21) cm(-2) dominating the cosmic H I mass density.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/980c20ec8431b63b460a357e26074029c2c22c17

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Citations in the corpus

• ON THE (NON)EVOLUTION OF H i GAS IN GALAXIES OVER COSMIC TIME (2008, methodology): “In Figure 1b, we also present the cumulative f(NHI, X) function for H I disks in the local universe, as estimated from 21cm observations (Zwaan et al. 2005b).”
• Column density distribution and cosmological mass density of neutral gas: Sloan Digital Sky Survey-III Data Release 9 (2012, methodology): “The measurement by Braun (2012) is based on only three galaxies, and although the high-column density end of f (NHI, χ) seems to be well constrained, this may not be true at low N(H i) (Zwaan et al. 2005).”
• Reionization and Cosmology with 21-cm Fluctuations (2009, background): “Their clustering (Cooke et al. 2006) and abundance (Zwaan et al. 2005), as well as theoretical expectations (Nagamine et al. 2007) suggest that DLAs are housed within galactic mass systems.”
• Damped Lyman α systems in galaxy formation simulations (2008, background): “The total DLA cross-section is thought to be evenly spread through many orders of magnitude of parent halo mass (Gardner et al. 1997a,b); observations of low redshift DLAs appear to confirm such a view (Zwaan et al. 2005).”
• Average extinction curves and relative abundances for quasi-stellar object absorption-line systems at 1 ≤zabs < 2 (2006, result): “(v) Zwaan et al. (2005) have shown that the properties and incidence rates of DLAs are in good agreement with DLAs originating in galaxies of various morphological types like the local galaxies.”
• The ESO UVES advanced data products quasar sample: II. Cosmological evolution of the neutral gas mass density (2013, background): “The Zwaan et al. (2005b) results come from 21-cm emission of atomic hydrogen ofz = 0 analogues to DLAs.”
• The ATLAS3D project - XIII. Mass and morphology of H I in early-type galaxies as a function of environment (2011, methodology): “Therefore, we assume the same flat slope found for spiral galaxies (α ∼ −1).5 We note that, although in different contexts, several authors have successfully parametrized the distribution of N(H I) in galaxies using a Schechter function (e.g. Zwaan et al. 2005b).”
• The physics of the intergalactic medium (2007, background): “The incidence rate and column density distribution of DLAs at z 1 is comparable to those of low redshift galaxies directly measured in H I (Zwaan et al., 2005).”
• Evolution of the cosmological mass density of neutral gas from Sloan Digital Sky Survey II - Data Release 7 (2009, methodology): “TheΓ-function fit to the frequency distribution obtained by Zwaan et al. (2005b) from 21-cm observations atz = 0 is also indicated as a solid grey line for direct comparison.”
• On the evolution of the H i column density distribution in cosmological simulations (2012, background): “The data points with error bars show results from high-redshift (z = 1.7− 5.5) QSO absorption line studies and the orange filled circles show the fitting function reported by Zwaan et al. (2005) based on 21-cm observations of nearby galaxies.”