Limits on the Time Variation of the Electromagnetic Fine-Structure Constant in the Low Energy Limit from Absorption Lines in the Spectra of Distant Quasars

We present the results of a detailed many-multiplet analysis performed on a new sample of Mg ii systems observed in high quality quasar spectra obtained using the Very Large Telescope. The weighted mean value of the variation in derived from our analysis over the redshift range 0. 42. 3 is /= (-0. 060. 06) 10^-5. The median redshift of our sample (z1. 55) corresponds to a look-back time of 9. 7 Gyr in the most favored cosmological model today. This gives a 3 limit, -2. 510^-16 (/) +1. 210^-16 yr^-1, for the time variation of, that forms the strongest constraint obtained based on high redshift quasar absorption line systems.