A new constraint on the time dependence of the proton-to-electron mass ratio

Analysis of the Q 0347-383 and Q 0405-443 spectra

¹ Ioffe Physical Technical Institute, Polytekhnicheskaya 26, 194021 Saint-Petersburg, Russia e-mail: iav@astro.ioffe.rssi.ru
² Institut d'Astrophysique de Paris – CNRS, 98bis Boulevard Arago, 75014 Paris, France e-mail: ppetitje@iap.fr
³ LERMA, Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France
⁴ Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003-9305, USA
⁵ IUCAA, Post Bag 4, Ganeshkhind, Pune 411007, India
⁶ European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Vitacura, Santiago, Chile

Received: 2 January 2004
Accepted: 10 May 2005

Abstract

A new limit on the possible cosmological variation of the proton-to-electron mass ratio is estimated by measuring wavelengths of H₂ lines of Lyman and Werner bands from two absorption systems at and 3.0249 in the spectra of quasars Q 0405-443 and Q 0347-383, respectively. Data are of the highest spectral resolution (R = 53 000) and S/N ratio (3070) for this kind of study. We search for any correlation between z_i, the redshift of observed lines, determined using laboratory wavelengths as references, and K_i, the sensitivity coefficient of the lines to a change of μ, that could be interpreted as a variation of μ over the corresponding cosmological time. We use two sets of laboratory wavelengths, the first one, Set (A) (Abgrall et al. 1993, J. Mol. Spec., 157, 512), based on experimental determination of energy levels and the second one, Set (P) (Philip et al. 2004, Can. J. Chem., 82, 713), based on new laboratory measurements of some individual rest-wavelengths. We find /μ = (3.05 ± 0.75)  10^-5 for Set (A), and /μ = (1.65 ± 0.74)  10^-5 for Set (P). The second determination is the most stringent limit on the variation of μ over the last 12 Gyr ever obtained. The correlation found using Set (A) seems to show that some amount of systematic error is hidden in the determination of energy levels of the H₂ molecule.