EDP Sciences
Free access
Issue
A&A
Volume 422, Number 2, August I 2004
Page(s) 523 - 526
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20041030


A&A 422, 523-526 (2004)
DOI: 10.1051/0004-6361:20041030

The ratio of the C IV $\lambda\lambda$1548,1550 rest-wavelengths from high-redshift QSO absorption lines

P. Petitjean1, 2 and B. Aracil1, 3

1  Institut d'Astrophysique de Paris, 98bis Boulevard Arago, 75014 Paris, France
    e-mail: petitjean@iap.fr
2  LERMA, Observatoire de Paris-Meudon, 61 avenue de l'Observatoire, 75014 Paris, France
3  Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003-9305, USA

(Received 6 October 2003 / Accepted 3 May 2004)

Abstract
We use very high quality VLT-UVES quasar spectra obtained in the course of the ESO Large Programme "Cosmic evolution of the Intergalactic Medium", to show that the ratio of the C IV doublet rest-wavelengths published in the literature and widely used is not consistent with high-redshift observations. From the analysis of 106 C IV systems we obtain: $\lambda_2$/ $\lambda_1=1.00166228\pm0.13\times10^{-6}$. A similar analysis on 28 Si IV systems shows that the observed ratio is consistent with the well known Si IV $\lambda\lambda$1393,1402 wavelengths. Using Si IV lines to calibrate the C IV lines in 11 systems, we find $\lambda_{1,2} = 1548$.2049 and  $1550.7785\pm0.0012$ Å which is consistent with the Griesmann & Kling (2000) laboratory wavelengths. The precision on the doublet ratio is better because of the large number of C IV systems available for the measurement. This shows that it is possible to perform atomic physics measurements using high redshift astrophysical data.


Key words: cosmology: observations -- galaxies: intergalactic medium -- galaxies: halos -- galaxies: quasars: absorption lines

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