The UVES Large Program for testing fundamental physics - III. Constraints on the fine-structure constant from 3 telescopes

Abstract

Large statistical samples of quasar spectra have previously indicated possible cosmological variations in the fine-structure constant, $\alpha$. A smaller sample of higher signal-to-noise ratio spectra, with dedicated calibration, would allow a detailed test of this evidence. Towards that end, we observed equatorial quasar HS 1549$+$1919 with three telescopes: the Very Large Telescope, Keck and, for the first time in such analyses, Subaru. By directly comparing these spectra to each other, and by `supercalibrating' them using asteroid and iodine-cell tests, we detected and removed long-range distortions of the quasar spectra's wavelength scales which would have caused significant systematic errors in our $\alpha$ measurements. For each telescope we measure the relative deviation in $\alpha$ from the current laboratory value, $\Delta \alpha /\alpha$, in 3 absorption systems at redshifts $z_{\mathrm{abs}}=1.143$, 1.342, and 1.802. The nine measurements of $\Delta \alpha /\alpha$ are all consistent with zero at the 2-$\sigma$ level, with 1-$\sigma$ statistical (systematic) uncertainties 5.6--24 (1.8--7.0) parts per million (ppm). They are also consistent with each other at the 1-$\sigma$ level, allowing us to form a combined value for each telescope and, finally, a single value for this line of sight: $\Delta \alpha /\alpha =-5.4\pm 3.3_{\mathrm{stat}}\pm 1.5_{\mathrm{sys}}$ ppm, consistent with both zero and previous, large samples. We also average all Large Programme results measuring $\Delta \alpha /\alpha =-0.6\pm 1.9_{\mathrm{stat}}\pm 0.9_{\mathrm{sys}}$ ppm. Our results demonstrate the robustness and reliability at the 3 ppm level afforded by supercalibration techniques and direct comparison of spectra from different telescopes.

24 pages, 11 figures, 9 tables

References in corpus (4)

• Spatial variation in the fine-structure constant -- new results from VLT/UVES
• Selection of ThAr lines for wavelength calibration of echelle spectra and implications for variations in the fine-structure constant
• A new measure of Delta alpha/alpha at redshift z = 1.84 from very high resolution spectra of Q1101-264
• UVES radial velocity accuracy from asteroid observations. Implications for the fine structure constant variability

Cited by in corpus (6)

• Impact of instrumental systematic errors on fine-structure constant measurements with quasar spectra
• Evolution of the fine-structure constant in runaway dilaton models
• Fundamental cosmology in the E-ELT era: The status and future role of tests of fundamental coupling stability
• Fine-structure constant constraints on dark energy
• Further consistency tests of the stability of fundamental couplings
• Fundamental Cosmology from Precision Spectroscopy: II. Synergies with supernovae