The ratio of the C IV1548,1550 rest-wavelengths from high-redshift QSO absorption lines ^*

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: /. A similar analysis on 28 Si iv systems shows that the observed ratio is consistent with the well known Si iv1393,1402 wavelengths. Using Si iv lines to calibrate the C iv lines in 11 systems, we find .2049 and  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.