2009 (IPP)
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Item Optical identification of XMM sources in the CFHTLS(2009-05-01) Stalin, C. S.; Petitjean, Patrick; Srianand, R.; et al.We summarize the attempts by our group and others to derive constraints on variations of fundamental constants over cosmic time using quasar absorption lines. Most upper limits reside in the range 0.5 1.5 10 5 at the 3 level over a redshift range of approximately 0:5 2:5 for the fine-structure constant, , the proton-to-electron mass ratio, and a combination of the proton gyromagnetic factor and the two previous constants, gp( 2= ) , for only one claimed variation of . It is therefore very important to perform new measurements to improve the sensitivity of the numerous methods to at least <0.1 10 5 which should be possible in the next few years. Future instrumentations on ELTs in the optical and/or ALMA, EVLA and SKA pathfinders in the radio will undoutedly boost this field by allowing to reach much better signal-to-noise ratios at higher spectral resolution and to perform measurements on molecules in the ISM of high redshift galaxiItem Damped and sub-damped Lyman-alpha absorbers in z > 4 QSOs(2009-10-01) Guimaraes, R.; Petitjean, PatrickWe present the results of a survey for damped (DLA, log N(H i) > 20.3) and sub-damped Lyman-α systems (19.5 < log N(H i) < 20.3) at z > 2.55 along the lines-of-sight to 77 quasars with emission redshifts in the range 4 < zem < 6.3. Intermediate resolution (R ∼ 4300) spectra have been obtained with the Echellette Spectrograph and Imager (ESI) mounted on the Keck telescope. A total of 100 systems with log N(H i) > 19.5 are detected of which 40 systems are damped Lyman-α systems for an absorption length of ∆X = 378. About half of the lines of sight of this homogeneous survey have never been investigated for DLAs.We study the evolution with redshift of the cosmological density of the neutral gas and find, consistently with previous studies at similar resolution, that ΩDLA,HI decreases at z > 3.5. The overall cosmological evolution of ΩHI shows a peak around this redshift. The H i column density distribution for log N(H i) ≥ 20.3 is fitted, consistently with previous surveys, with a single power-law of index α ∼ -1.8±0.25. This power-law overpredicts data at the high-end and a second, much steeper, power-law (or a gamma function) is needed. There is a flattening of the function at lower H i column densities with an index of α ∼ −1.4 for the column density range log N(H i) = 19.5−21. The fraction of H i mass in sub-DLAs is of the order of 30%. The H i column density distribution does not evolve strongly from z ∼ 2.5 to z ∼ 4.5.Item Complete sample of 21-cm absorbers at z ~ 1.3: Giant Metrewave Radio Telescope Survey Using Mg II Systems(2009-04-01) Gupta, N.; Srianand, R.; Petitjean, Patrick; et al.We present the results of a systematic Giant Metrewave Radio Telescope (GMRT) survey of 21-cm absorption in a representative and unbiased sample of 35 strong Mg ii systems in the redshift range: zabs∼1.10−1.45, 33 of which have Wr ≥1˚ A. The survey using ∼400 hrs of telescope time has resulted in 9 new 21-cm detections and stringent 21-cm optical depth upper limits (median 3σ optical depth per 10 kms−1 of 0.017) for the remaining 26 systems. This is by far the largest number of 21-cm detections from any single survey of intervening absorbers. Prior to our survey no intervening 21-cm system was known in the above redshift range and only one system was known in the redshift range 0.7 ≤ z ≤ 1.5. We discuss the relation between the detectability of 21-cm absorption and various properties of UV absorption lines. We show that if Mg ii systems are selected with the following criteria, Mg ii doublet ratio ≤1.3 and Wr(Mg i)/Wr(Mg ii) ≥ 0.3, then a detection rate of 21-cm absorption up to 90% can be achieved. We estimate n21, the number per unit redshift of 21-cm absorbers with Wr(Mg ii) > Wo and integrated optical depth T21 > To and show that n21 decreases with increasing redshift. In particular, for Wo = 1.0 ˚ A and To > 0.3 km s−1, n21 falls by a factor 4 from < z > = 0.5 to < z > = 1.3. The evolution seems to be stronger for stronger Mg ii systems. Using a subsample of systems for which high frequency VLBA images are available, we show that the effect is not related to the structure of the background radio sources and is most probably due to the evolution of the cold neutral medium filling factor in Mg ii systems. We find no correlation between the velocity spread of the 21-cm absorption feature and Wr(Mg ii) at z ∼ 1.3