Nature and Properties of sub-DLAs (absorbers with 10^19≤ N(HI) ≤ 2 * 10^20 cm^-2)
Source: Astrophysics and Space Science, Volume 281, Numbers 1-2, July 2002 , pp. 543-544(2)
Abstract:Quasar absorbers provide an alternative approach to the study of galaxies. In particular, the detection of high-column density systems allow to measure the cosmological evolution of the neutral gas mass and metals in the Universe. At z <3.5, 90% of the HI mass is in damped Lyα systems (DLAs). But it has been suggested that at z > 3.5, 45% of the HI lies in systems below the traditional DLA definition (2 × 10^20 cm^-2), in `sub-DLAs' with 10^19 < N(HI) < 2 × 10^20 cm^-2. Here we present a sample of sub-DLAs issued from UVES archive quasar spectra. We have measured the sub-DLA number density redshift evolution and directly establish their column density distribution function. We have also undertaken a detailed metal abundance analysis of this class of absorbers to compare with the characteristics of the well studied DLAs.
Document Type: Regular Paper
Publication date: July 1, 2002