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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 Collimated flow driven by radiative pressure from the nucleus of quasar Q 1511 + 091(2011-07-06) Srianand, R.; Petitjean, Patrick; Ledoux, C.; et al.High velocity outflows from quasars are revealed by the absorption signatures they produce in the spectrum of the quasar. Clues on the nature and origin of these flows are important for our understanding of the dynamics of gas in the central regions of the Active Galactic Nucleus (AGNs) but also of the metal enrichment of the intergalactic space. Line radiation pressure has often been suggested to be an important process in driving these outflows, however no convincing evidence has been given so far. Here we report observation of a highly structured flow, toward Q 1511+091, where the velocity separations between distinct components are similar to O vi, N v and C iv doublet splittings with some of the profiles matching perfectly. This strongly favors the idea that the absorbing clumps originate at similar physical location and are driven by radiative acceleration due to resonance lines. The complex absorption can be understood if the flow is highly collimated so that the different optically thick clouds are aligned and cover the same region of the background source. One component shows saturated H i Lyman series lines together with absorptions from excited levels from C ii and Si ii but covers only 40% of the source of continuum. The fact that clouds cover only part of the small continuum source implies that the flow is located very close to it.Item Outflowing material in the Zem=4.92 BAL QSO SDSS J160501.21 - 011220.0(2011-07-05) Gupta, Neeraj; Srianand, R.; Petitjean, Patrick; et al.We present the analysis of broad absorption lines (BALs) seen in the spectrum of the zem ≃4.92 QSO SDSS J160501.21-011220.0. Our high spectral resolution UVES spectrum shows two well detached absorption line systems at zabs= 4.685 and 4.855. The system at zabs= 4.855 covers the background source completely suggesting that the gas is located outside the broad emission line region. On the contrary the system at zabs= 4.685, which covers only on the continuum source, has a covering factor of the order of 0.9. Physical conditions are investigated in the BAL system at zabs= 4.855 using detailed photoionization models. The observed H i absorption line together with the limits on C ii and Si ii absorptions suggest that 16 < log N(H i) (cm−2 ) < 17 in this system. Comparison with models show that the observed column densities of N v , Si iv and C iv in this system require that nitrogen is underabundant by more than a factor 3 compared to silicon if the ionizing radiation is similar to a typical QSO spectrum. This is contrary to what is usually derived for the emission line gas in QSOs. We show that the relative suppression in the N v column density can be explained for Solar abundance ratios or abundance ratios typical of Starburst abundances if an ionizing spectrum devoid of X-rays is used instead. Thus, if the composition of BAL is like that of the emission line regions it is most likely that the cloud sees a spectrum devoid of X-rays similar to what we observe from this QSO. This is consistent with the fact that none of our models have high Compton optical depth to remove X-rays from the QSO. Similar arguments lead to the conclusion that the system at zabs= 4.685 as well is not Compton thick. Using simple Eddington arguments we show that the mass of the central black hole is ∼ 8 × 108 M⊙. This suggests that the accretion onto a seed black hole must have started as early as z = 11.Item Probing the time-variation of the fine-structure constant: Results based on Si IV doublets from a UVES sample(2011-07-06) Chand, Hum; Petitjean, Patrick; Srianand, R.; et al.We report a new constraint on the variation of the fine-structure constant based on the analysis of 15 Si iv doublets selected from a ESO-UVES sample. We find ∆α/α = (+0.15 ± 0.43) × 10−5 over a redshift range of 1.59 ≤ z ≤ 2.92 which is consistent with no variation in α. This result represents a factor of three improvement on the constraint on ∆α/α based on Si iv doublets compared to the published results in the literature. The alkali doublet method used here avoids the implicit assumptions used in the many-multiplet method that chemical and ionization inhomogeneities are negligible and isotopic abundances are close to the terrestrial value.Item Probing the cosmological variation of the fine-structure constant:Results on VLT-UVES sample(2011-07-06) Chand, Hum; Srianand, R.; Petitjean, Patrick; et al.Abstract. Development of fundamental physics relies on the constancy of various fundamental quantities such as the fine structure constant. Detecting or constraining the possible time variations of these fundamental physical quantities is an important step toward a complete understanding of basic physics. High quality absorption lines seen in the spectra of distant QSOs allow one to probe time variations of several of these quantities. Here we present the results from a detailed many-multiplet analysis, to detect the possible variation of fine-structure constant, performed using high signal-to-noise ratio, (∼70 per pixel), high spectral resolution (R ≥45000) observations of 23 Mg ii systems detected toward 18 QSOs in the redshift range 0.4 ≤ z ≤ 2.3 obtained using UVES at the VLT. We validate our procedure and define the selection criteria that will avoid possible systematics using detail analysis of simulated data set. The spectra of Mg ii doublets and Fe ii multiplets are generated considering variations in α and specifications identical to that of our UVES spectra. We show our Voigt profile fitting code recovers the variation in α very accurately when we use single component systems and multiple component systems that are not heavily blended. Spurious detections are frequently seen when we use heavily blended systems or the systems with very weak lines. Thus we avoided heavily blended systems and the systems with Fe ii column density < 2×1012 cm−2 while analysing the UVES data. To make the analysis transparent and accessible to the community for critical scrutiny all the steps involved in the analysis are presented in detail. The weighted mean value of the variation in α obtained from our analysis over the redshift range 0.4 ≤ z ≤ 2.3 is ∆α/α = (−0.06 ± 0.06) × 10−5 . The median redshift of our sample is 1.55 and corresponds to a look-back time of 9.7 Gyr in the most favored cosmological model today. The 3σ upper limit on the time variation of α is −2.5 × 10−16 yr −1 ≤ (∆α/α∆t) ≤ +1.2 × 10−16 yr −1 . To our knowledge this is the strongest constraint from quasar absorption line studies till date.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.