Sub-Dlas Implications for Cosmological Evolution of Metals.
Abstract
Quasar absorbers constitute powerful observational tools to measure the cosmological evolution of the neutral gas and metals. At z<3.5 90% of the HI mass is in damped Ly-alpha systems (DLAs). But it has been suggested that at z>3.5 45% of the HI lies in systems below the traditional DLA definition in ``sub-DLAs'' with 1019 < N(HI) < 2 * 1020 cm-2. We took advantage of the ESO-UVES archive quasar spectra to build a homogeneous sample of 13 sub-DLAs. These data are used to directly establish the column density distribution function down to N(HI) = 1019 cm-2. Some of the kinematical properties of the quasar absorbers are also found to be correlated with metallicity as traced by [Fe/H]. Possible explanations for this correlation will be proposed. The analyse of the sub-DLA sample also include the detailed metal abundance determination together with a full treatment of the ionisation correction. The results complemented with a database of over 70 metallicity measurements in DLAs from the literature are found to affect the cosmological evolution of metals as traced by quasar absorbers. Future programs aiming at extending such studies towards higher redshifts will be briefly presented.
- Publication:
-
IAU Joint Discussion
- Pub Date:
- 2003
- Bibcode:
- 2003IAUJD..15E...9P