Issue |
A&A
Volume 391, Number 3, September I 2002
|
|
---|---|---|
Page(s) | 801 - 807 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361:20020843 | |
Published online | 09 August 2002 |
New detections of Mn, Ti and Mg in damped Lyα systems: Toward reconciling the dust/nucleosynthesis degeneracy*
1
European Southern Observatory, Karl-Schwarzschildstr. 2, 85748 Garching bei München, Germany e-mail: mdessaug@eso.org; sdodoric@eso.org
2
Observatoire de Genève, 1290 Sauverny, Switzerland
3
The Observatories of the Carnegie Institute of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA e-mail: xavier@ociw.edu
4
Hubble Fellow
Corresponding author: M. Dessauges-Zavadsky, mdessaug@eso.org
Received:
12
February
2002
Accepted:
4
June
2002
We have combined new high resolution UVES-VLT observations of a sample of four damped Lyα
systems (DLAs) at redshifts between with the existing HIRES-Keck spectra
to undertake a comprehensive study of their physical conditions and their abundances of up to 15
elements. In this paper, we present abundance measurements for Mn, Ti and Mg which are among the
first presented in the literature at these redshifts. We confirm the underabundance of Mn with
respect to Fe as observed in lower redshift DLAs and a trend with decreasing metallicity very
similar to the one observed in Galactic metal-poor stars. This agreement between the Mn/Fe ratios in
DLAs and in Galactic stars suggests that the DLAs and the Milky Way share some similarities in their
star formation histories. However, these similarities must be cautiously interpreted and investigated
in light of all of the elements observed in the DLAs. We have obtained a first measurement and a
significant upper limit of the Ti abundance at
from the
lines at
Å, and we discuss how the relative abundance of this highly depleted
element can be used to prove unambiguously any enhancement of the abundance of the α-elements
relative to Fe-peak elements. We present the abundances of Mg for two DLAs in addition to the single
Mg measurement existing in the literature. Contrary to the trend expected from differential
depletion, the [Mg/Si, S] ratios tend to be over-solar. The effect is at the level of the measurement
errors, but worth investigating in a larger sample because it could be suggestive of a peculiar
nucleosynthesis effect.
Key words: cosmology: observations - galaxies: abundances / galaxies: evolution / quasars: absorption lines
© ESO, 2002
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