Hints of star formation at z : The chemical abundances of the DLA system in the QSO BRI 1202-0725 (z )

Free access article

Issue		A&A Volume 415, Number 3, March I 2004


Page(s)		879 - 884
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20034584

A&A 415, 879-884 (2004)
DOI: 10.1051/0004-6361:20034584

Hints of star formation at z $\mathsf{>6}$ : The chemical abundances of the DLA system in the QSO BRI 1202-0725 (z $\mathsf{_{abs}=4.383}$ )

V. D'Odorico and P. Molaro

INAF - Osservatorio Astronomico di Trieste, via G.B. Tiepolo, 11, 34131 Trieste, Italy
(Received 23 July 2003 / Accepted 30 October 2003 )

Abstract
The Damped Ly- $\alpha$ (DLA) absorber at redshift $z_{\rm abs}=4.383$ observed toward QSO BRI 1202-0725 is studied by means of high resolution (FWHM $\approx 7$ km s ^-1) VLT-UVES spectra. We refine a previously determined Si abundance and derive with confidence abundances for C, N and O which are poorly known in DLAs. The [O/Fe] ratio is ~ 0.6, but we cannot establish if iron is partially locked into dust grains. The [C/Fe] $=0.08\pm 0.13$ and [Si/C] $=0.31\pm0.07$ . [N/O] and [N/Si] are about -1, which is consistent with the majority of DLAs. This value is much larger than the one observed for the DLA toward QSO J 0307-4945 at $z_{\rm abs} = 4.466$ . The current interpretation of the bimodal distribution of N abundances in DLAs implies that large [ N/ $\alpha$ ] values correspond to relatively old systems. Adopting a scale time of 500 Myrs for full N production by intermediate mass stars, the onset of star formation in our DLA took place already at redshift > 6.

Key words: galaxies: abundances -- galaxies: high-redshift -- galaxies: quasars: absorption lines -- cosmology: observations

Offprint request: V. D'Odorico, dodorico@sissa.it

SIMBAD Objects

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.