UVES observations of a damped Ly alpha system at z(abs)=4.466 towards the quasar APM BR J0307-4945

Citation
M. Dessauges-zavadsky et al., UVES observations of a damped Ly alpha system at z(abs)=4.466 towards the quasar APM BR J0307-4945, ASTRON ASTR, 370(2), 2001, pp. 426-435
Citations number
50
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMY AND ASTROPHYSICS
ISSN journal
0004-6361 → ACNP
Volume
370
Issue
2
Year of publication
2001
Pages
426 - 435
Database
ISI
SICI code
0004-6361(200105)370:2<426:UOOADL>2.0.ZU;2-C
Abstract
We present the first high-resolution (6.2 to 7.7 km s(-1) FWHM) spectra of the APM BR J0307-4945 quasar at z(em) = 4.73 obtained with UVES on the 8.2 m VLT Kueyen telescope. We focus our analysis on a damped Ly alpha (DLA) sy stem at z(abs) = 4.466 with a neutral hydrogen column density N(H1) = (4.68 +/- 0.97) 10(20) cm(-2) It is the most distant DLA system known to the pre sent date, observed when the age of the universe was only 1.3 Gyr. It shows complex low- and high-ionization line profiles spanning approximate to 240 and 300 km s(-1) in velocity space respectively. We derive accurate abunda nces for N, O, Al, Si and Fe, and place a lower limit on C and an upper lim it on Ni: [N/H] = -3.07 +/- 0.15, [O/H] = -1.63 +/- 0.19, [Al/H] = -1.79 +/ - 0.11, [Si/H] = -1.54 +/- 0.11, [Fe/H] = -1.97 +/- 0.19, [C/H] > -1.63 and [Ni/H] < -2.35. The derived high metallicity, <similar to>1/90 solar, show s that this very young absorber (<1.3 Gyr) has already experienced a signif icant metal enrichment. The [O/Si] ratio is nearly solar suggesting a limit ed amount of dust, the relative [Si. O/Fe] abundance ratios show a similar enhancement as observed in the Milky Way stars with comparable metallicitie s, and the [N/O] ratio is very low. All these results point to an enrichmen t pattern dominated by type II supernovae which suggests a Milky Way type e volutionary model.