https://doi.org/10.1140/epjst/e2008-00818-4
Bounds on the fine structure constant variability from Fe ii absorption lines in QSO spectra
1
Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34131 Trieste, Italy
2
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
3
Ioffe Physico-Technical Institute, St. Petersburg, Russia
Corresponding author: molaro@oats.inaf.it
The Single Ion Differential α Measurement (SIDAM) method for measuring Δα/α and its figures of merit are illustrated together with the results produced by means of Fe ii absorption lines of QSO intervening systems. The method provides Δα/α = -0.12 ±1.79 ppm (parts-per-million) at zabs = 1.15 towards HE 0515-4414 and Δα/α = 5.66±2.67 ppm at zabs = 1.84 towards Q 1101-264, which are so far the most accurate measurements for single systems. SIDAM analysis for 3 systems from the Chand et al. [1] sample provides inconsistent results which we interpret as due to calibration errors of the Chand et al. data at the level ≈10 ppm. In one system evidence for photo-ionization Doppler shift between Mg ii and Fe ii lines is found. This evidence has important bearings on the Many Multiplet method where the signal for Δα/αvariability is carried mainly by systems involving Mg ii absorbers. Some correlations are also found in the Murphy et al. [10] sample which suggest larger errors than previously reported. Thus, we consider unlikely that both the Chand et al. and Murphy et al. datasets could provide an estimate of Δα/α with an accuracy at the level of 1 ppm. A new spectrograph like the ESPRESSO project will be crucial to make progress in the astronomical determination of Δα/α.
© EDP Sciences, Springer-Verlag, 2008
