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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 308689.0, MPI für Astronomie / Publikationen_mpia
First detection of Na I D lines in high-redshift damped Lya Systems
Authors:Kondo, S.; Kobayashi, N.; Minowa, Y.; Tsujimoto, T.; Churchill, C. W.; Takato, N.; Iye, M.; Kamata, Y.; Terada, H.; Pyo, T.-S.; Takami, H.; Hayano, Y.; Kanzawa, T.; Saint-Jacques, D.; Gaessler, W.; Oya, S.; Nedachi, K.; Tokunaga, A.
Date of Publication (YYYY-MM-DD):2006
Journal Abbrev.:The Astrophysical Journal
Start Page:667
End Page:674
Audience:Not Specified
Abstract / Description:An NIR (1.18-1.35 mum) high-resolution spectrum of the gravitationally lensed QSO APM 08279+5255 was obtained with the Subaru Telescope IRCS using the AO system. We have detected strong Na I D lambdalambda5891, 5897 doublet absorption in high-redshift DLAs at zabs=1.062 and 1.181, confirming the presence of Na I, which was first reported for the rest-frame UV Na I lambdalambda3303.3, 3303.9 doublet by Petitjean et al. This is the first detection of Na I D absorption in a high-redshift (z>1) DLA. We have also detected a new Na I component in the zabs=1.062 DLA and four new components in the zabs=1.181 DLA. Using an empirical relationship between Na I and H I column density, we found that all components have large H I column density (logNHI [cm-2]>~20.3), so each component is classified as DLA absorption. We also detected strong Na I D absorption associated with a Mg II system at zabs=1.173. Because no other metal absorption lines were detected in this system at the velocity of the Na I absorption in previously reported optical spectra, we infer that this Na I absorption cloud probably appeared in the line of sight toward the QSO after the optical observation. This newly found cloud is likely to be a DLA based on its large estimated H I column density. We found that the NNaI/NCaII ratios in these DLAs are systematically smaller than those observed in the Galaxy; they are more consistent with the ratios seen in the LMC. This is consistent with dust depletion generally being smaller in lower metallicity environments. However, all five clouds of the zabs=1.181 system have a high NNaI/NCaII ratio, which is characteristic of cold dense gas. We tentatively suggest that the host galaxy of this system may be the most significant contributor to the gravitational lens toward APM 08279+5255. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.
Free Keywords:Galaxies: Formation; Cosmology: Gravitational Lensing; Galaxies: Intergalactic Medium; Galaxies: Quasars: Absorption Lines; Galaxies: Quasars: Individual: Alphanumeric: APM 08279+5255
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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