First Detection of Na I D Lines in High-Redshift Damped Lyα Systems

摘要: An NIR (1.18–1.35 � m) high-resolution spectrum of the gravitationally lensed QSO APM 08279+5255 was obtained with Subaru Telescope IRCS using AO system. We have detected strong Na i D kk5891, 5897 doublet absorption in high-redshift DLAs at zabs ¼ 1:062 and 1.181, confirming presence ,w hich firstreportedfortherest-frameUVNaikk3303.3,3303.9doubletbyPetitjeanetal.ThisisthefirstdetectionofNa a (z > 1)DLA. also new Nai component thezabs 1:062DLA four components 1:181 DLA. Using an empirical relationship between H column density,wefoundthatallcomponentshavelargeHicolumndensity( logNH ½cm 2 k20:3),soeachcomponentis classified as DLA absorption. associated Mg ii system 1:173. Because no other metal lines were this velocity previously reported optical spectra, we infer that cloud probably appeared line sight toward after observation. This newly found is likely to be based on its large estimated density. NNa i/NCa ratios these are systematically smaller than those observed Galaxy; they more consistent seen LMC. dust depletion generally being lower metallicity environments. However, all five clouds high ratio, which characteristic cold dense gas. tentatively suggest host galaxy may most significant contributor gravitational lens 08279+5255. Subject headings: galaxies: formation — lensing intergalactic medium quasars: individual (APM 08279+5255)