Thursday, July 4, 2013

1307.0678 (Tayyaba Zafar et al.)

The ESO UVES Advanced Data Products Quasar Sample - I. Dataset and New N_HI Measurements of Damped Absorbers    [PDF]

Tayyaba Zafar, Attila Popping, Celine Peroux
We present here a dataset of quasars observed with the Ultraviolet Visual Echelle Spectrograph (UVES) on the VLT and available in the ESO UVES Advanced Data Products archive. The sample is made up of a total of 250 high resolution quasar spectra with emission redshifts ranging from 0.191 < z_em <6.311. The total UVES exposure time of this dataset is 1560 hours. Thanks to the high resolution of UVES spectra, it is possible to unambiguously measure the column density of absorbers with damping wings, down to N_HI > 10^{19} cm^{-2}, which constitutes the sub-damped Lya absorber (sub-DLA) threshold. Within the wavelength coverage of our UVES data, we find 150 damped Lya systems (DLAs)/sub-DLAs in the range 1.5 < z_abs < 4.7. Of these 150, 93 are DLAs and 57 are sub-DLAs. An extensive search in the literature indicates that 6 of these DLAs and 13 of these sub-DLAs have their N_HI measured for the first time. Among them, 10 are new identifications as DLAs/sub-DLAs. For each of these systems, we obtain an accurate measurement of the HI column density and the absorber's redshift in the range 1.7 < z_abs < 4.2 by implementing a Voigt profile-fitting algorithm. These absorbers are further confirmed thanks to the detection of associated metal lines and/or lines from members of the Lyman series. In our data, a few quasars' lines-of-sight are rich. An interesting example is towards QSO J0133+0400 (z_em = 4.154) with six DLAs and sub-DLAs reported.
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