Browsing by Author "Ivanchik, A."

Now showing 1 - 2 of 2

New constraint on the time dependence of the proton-to-electron mass ratio. Analysis of the Q 0347-383 and Q 0405-443 spectra
(2005-07-01) Ivanchik, A.; Srianand, R.; Varshalovich, D.
A new limit on the possible cosmological variation of the proton-to-electron mass ratio µ = mp/me is estimated by measuring wavelengths of H2 lines of Lyman and Werner bands from two absorption systems at zabs = 2.5947 and 3.0249 in the spectra of quasars Q 0405−443 and Q 0347−383, respectively. Data are of the highest spectral resolution (R = 53000) and S/N ratio (30÷70) for this kind of study. We search for any correlation between zi, the redshift of observed lines, determined using laboratory wavelengths as references, and Ki, 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), based on experimental determination of energy levels and the second one, Set (P) (Philip et al. 2004), based on new laboratory measurements of some individual rest-wavelengths. We ﬁnd ∆µ/µ = (3.05±0.75)×10−5 for Set (A), and ∆µ/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 Gyrs 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.
Time dependence of the proton-to-electron mass ratio
(2011-07-06) Petitjean, Patrick; Ivanchik, A.; Srianand, R.; et al.
We have measured with high precision the position of 79 molecular hydrogen absorption lines of Lyman and Werner bands from two absorption systems at zabs = 2.594733 and 3.024899, in the spectra of quasars Q 0405–443 and Q 0347–383, respectively, in order to constrain the cosmological variation of the proton-to-electron mass ratio, µ = mp/me.Dataareof the highest spectral resolution (R = 53 000) and signal to noise ratio (S/N = 30–70) for such quasars. The absorption lines are not saturated and their proﬁles can be modelled as simple Gaussian functions. We ﬁnd a correlation between the observed redshift of the lines and the sensitivity of the line positions to a change in µ. This can be interpreted as a variation of µ with µ/µ = (2.97 ± 0.74) × 10−5 over the past ∼12 Gyrs. As this result is based on two systems one cannot rule out that unknown systematics could cause a false-alarm detection. Thus the result needs to be conﬁrmed with additional data. It is also very important to improve the accuracy of the laboratory wavelengths as the signiﬁcance of our result depends on the accuracy to which they are known.