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Item New measurement of sinc metallicity in a DLA at z ~ 3.35(2002-03-02) Peroux, C.; Petitjean, Patrick; Aracil, BastienWe present chemical abundance measurements in the zabs = 3.35045 Damped Lyman-α (DLA) system observed in the UVES spectrum of the BAL quasar BR 1117−1329. We measure a neutral hydrogen column density N(HI) = 6.9±1.7×1020 atoms cm−2 and derive mean abundances relative to solar: [Si/H] = −1.26 ± 0.13, [Fe/H] = −1.51±0.13, [Ni/H] = −1.57±0.13, [Cr/H] = −1.36±0.13, [Zn/H] = −1.18±0.13, [Al/H] > −1.25, [O/H] > −1.25 and [N/H] < −2.24. This is the third measurement of Zn, an element mildly depleted onto dust grain, at zabs > 3. The iron to zinc and chromium to zinc ratios, [Fe/Zn] = −0.33 ± 0.05 and [Cr/Zn] = −0.18 ± 0.05 demonstrate that the absorber has a low dust content. The nitrogen ratio [N/Si] < −0.98 suggests that the “secondary” N production process is taking place in this DLA. Finally, this absorber does not seem to present a convincing α- enhancement as shown by the α over Fe-peak element ratios: [Si/Fe] = 0.25±0.06, [Si/Cr] = 0.10 ± 0.06 and [Si/Zn] = −0.08 ± 0.06.Item Structure of the Mg II and damped Lyman- systems along the line of sight to APM 08279+5255(2000-05-24) Petitjean, Patrick; Aracil, Bastien; Srianand, R.; et al.A study of the absorption systems toward the gravitationally lensed quasar APM 08279+5255 is pre-sented.Most of the Mg ii systems in the redshift range z ∼ 1.2– 2.07, although saturated, show large residuals at the bot- tom of the lines. The most likely interpretation is that individual clouds within Mg ii halos do cover only one of the two brightest QSO images. The separation between the two lines of sight decreases from 1.7 to 0.7 h−1 75 kpc (qo = 0.5, zlens = 1) between z = 1.22 and z = 2.07. This reveals that Mg ii halos are made of a collection of clouds of radius smaller than about 1 h−1 75 kpc. Two strong Mg ii absorbers at zabs = 1.062 and 1.181 are studied in detail. This is the first time that the Na iλ3303 doublet is detected in such high redshift systems. To- gether with the detection of the Mg iλ2852 transition, this strongly constrains the physical characteristics of the gas. The N(Na i)/N(Mg i) ratio is found to be larger than unity, implying that the gas is cool and neutral. The Doppler parameters measured in individual and well de- tached components is probably as small as 1 km s−1. The column densities of Na i, Ca ii, Mg i, Ti ii, Mn ii and Fe ii observed at zabs = 1.1801 are very close to that observed along the line of sight towards 23 Ori in our Galaxy. The shape of the QSO continuum is consistent with attenu- ation by dust at z ∼ 1 (AV ∼ 0.5 mag). Altogether it is found that the H i column density at z = 1 is of the order of 1 to 5 1021 cm−2, the corresponding metallicity is in the range 1–0.3 Z⊙, the overall dust-to-metal ratio is about half that in our Galaxy and the relative deple- tion of iron, titanium, manganese and calcium is similar to what is observed in cool gas in the disk of our Galaxy. The objects associated with these two systems could both con-tribute to the lens together with another possible strong system at zabs = 1.1727 and the strong Lyman-α system at zabs = 2.974. The probable damped Lyman-α system at zabs = 2.974 has 19.8 < log N(H i) < 20.3. The transverse dimension of the absorber is larger than 200 h−1 75 pc. Column densities of Al ii, Fe ii, Si ii, C ii and O i indicate abundances rela- tive to solar of −2.31, −2.26, −2.10, −2.35 and −2.37 for, respectively, Fe, Al, Si, C and O (for log N(H i) = 20.3). These surprizingly similar values indicate that the amount of dust in the cloud is very small as are any deviations from relative solar abundances. It seems likely that the upper limits found for the zinc metallicity of several damped Lyman-α systems at z > 3 in previous surveys is indica- tive of a true cosmological evolution of the metallicity in individual systems.Item Relative abundance pattern along the profile of high redshift damped Lyman-alpha systems(2005-09-01) Rodriguez, E.; Ledoux, C.; Aracil, Bastien; et al.We investigate abundance ratios along the profiles of six high-redshift Damped Lyman-α systems, three of them beeing associated with H2 absorption. We use a new method to derive optical depths in each velocity pixel. The variations of the pixel abundance ratios are found to be remarquably small and usually smaller than a factor of two within a profile. This results holds when considering independent sub-clumps in the same system. Only in the components where H2 is detected is the depletion factor significantly enhanced. There is a strong correlation between [Fe/S] and [Si/S] ratios showing that the abundance ratio patterns are definitely related to the presence of dust. The depletion pattern is usually close to that seen in warm halo gas of our Galaxy.