2015ApJ...806...25S -
Astrophys. J., 806, 25 (2015/June-2)
Hubble Space Telescope observations of sub-damped Lyα absorbers at z < 0.5, and implications for galaxy chemical evolution.
SOM D., KULKARNI V.P., MEIRING J., YORK D.G., PEROUX C., LAUROESCH J.T., ALLER M.C. and KHARE P.
Abstract (from CDS):
We report observations of four sub-damped Lyα (sub-DLA) quasar absorbers at obtained with the Hubble Space Telescope Cosmic Origins Spectrograph. We measure the available neutrals or ions of C, N, O, Si, P, S, Ar, Mn, Fe, and/or Ni. Our data have doubled the sub-DLA metallicity samples at and improved constraints on sub-DLA chemical evolution. All four of our sub-DLAs are consistent with near-solar or super-solar metallicities and relatively modest ionization corrections; observations of more lines and detailed modeling will help to verify this. Combining our data with measurements from the literature, we confirm previous suggestions that the N(H i)-weighted mean metallicity of sub-DLAs exceeds that of DLAs at all redshifts studied, even after making ionization corrections for sub-DLAs. The absorber toward PHL 1598 shows significant dust depletion. The absorbers toward PHL 1226 and PKS 0439-433 show the S/P ratio consistent with solar, i.e., they lack a profound odd-even effect. The absorber toward Q0439-433 shows super-solar Mn/Fe. For several sub-DLAs at, [N/S] is below the level expected for secondary N production, suggesting a delay in the release of the secondary N or a tertiary N production mechanism. We constrain the electron density using Si ii* and C ii* absorption. We also report different metallicity versus relations for sub-DLAs and DLAs. For two sub-DLAs with detections of emission lines from the underlying galaxies, our measurements of the absorption-line metallicities are consistent with the emission-line metallicities, suggesting that metallicity gradients are not significant in these galaxies.
Abstract Copyright:
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Journal keyword(s):
galaxies: abundances - galaxies: evolution - quasars: absorption lines
CDS comments:
QSO J1103-2654 is a misprint for QSO J1103-2645.
Simbad objects:
22
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