We previously reported Keck telescope observations suggesting a smaller value of the fine structure constant $\alpha$ at high redshift. New Very Large Telescope (VLT) data, probing a different direction in the Universe, shows an inverse evolution; $\alpha$ increases at high redshift. Although the pattern could be due to as yet undetected systematic effects, with the systematics as presently understood the combined data set fits a spatial dipole, significant at the $4.2\sigma$ level, in the direction right ascension $17.5\pm 0.9$ h, declination $-58\pm 9$ deg. The independent VLT and Keck samples give consistent dipole directions and amplitudes, as do high and low redshift samples. A search for systematics, using observations duplicated at both telescopes, reveals none so far which emulate this result.

The primordial deuterium abundance is an important tracer of the fundamental physics taking place during big bang nucleosynthesis. It can be determined from absorption features along the line of sight to distant quasars. The quasar PKS 1937−1009 contains two absorptions systems that have been used to measure the primordial deuterium abundance, the lower redshift one being at z_abs = 3.256. New observations of this absorber are of a substantially higher signal-to-noise ratio and thus permit a significantly more robust estimate of the primordial deuterium abundance, leading to a D i/H i ratio of 2.45 ± 0.28 × 10⁻⁵. Whilst the precision of the new measurement presented here is below that obtained from the recent cosmological parameter measurements by the Planck Surveyor, our analysis illustrates how a statistical sample obtained using similarly high spectral signal-to-noise ratio can make deuterium a competitive and complementary cosmological parameter estimator and provide an explanation for the scatter seen between some existing deuterium measurements.

A new and automated method is presented for the analysis of high-resolution absorption spectra. Three established numerical methods are unified into one ‘artificial intelligence’ process: a genetic algorithm (Genetic Voigt Profile FIT, gvpfit); non-linear least-squares with parameter constraints (vpfit); and Bayesian model averaging (BMA). The method has broad application but here we apply it specifically to the problem of measuring the fine structure constant at high redshift. For this we need objectivity and reproducibility. gvpfit is also motivated by the importance of obtaining a large statistical sample of measurements of Δα/α. Interactive analyses are both time consuming and complex and automation makes obtaining a large sample feasible. In contrast to previous methodologies, we use BMA to derive results using a large set of models and show that this procedure is more robust than a human picking a single preferred model since BMA avoids the systematic uncertainties associated with model choice. Numerical simulations provide stringent tests of the whole process and we show using both real and simulated spectra that the unified automated fitting procedure out-performs a human interactive analysis. The method should be invaluable in the context of future instrumentation like ESPRESSO on the VLT and indeed future ELTs. We apply the method to the z_abs = 1.8389 absorber towards the z_em = 2.145 quasar J110325−264515. The derived constraint of Δα/α = 3.3 ± 2.9 × 10⁻⁶ is consistent with no variation and also consistent with the tentative spatial variation reported in Webb et al. and King et al.

We present an analysis of 23 absorption systems along the lines of sight towards 18 quasars in the redshift range of 0.4 ≤ z_abs ≤ 2.3 observed on the Very Large Telescope (VLT) using the Ultraviolet and Visual Echelle Spectrograph (UVES). Considering both statistical and systematic error contributions we find a robust estimate of the weighted mean deviation of the fine-structure constant from its current, laboratory value of Δα/α = (0.22 ± 0.23) × 10⁻⁵, consistent with the dipole variation reported in Webb et al. and King et al. This paper also examines modelling methodologies and systematic effects. In particular, we focus on the consequences of fitting quasar absorption systems with too few absorbing components and of selectively fitting only the stronger components in an absorption complex. We show that using insufficient continuum regions around an absorption complex causes a significant increase in the scatter of a sample of Δα/α measurements, thus unnecessarily reducing the overall precision. We further show that fitting absorption systems with too few velocity components also results in a significant increase in the scatter of Δα/α measurements, and in addition causes Δα/α error estimates to be systematically underestimated. These results thus identify some of the potential pitfalls in analysis techniques and provide a guide for future analyses.

Hot white dwarf stars are the ideal probe for a relationship between the fine-structure constant and strong gravitational fields, providing us with an opportunity for a direct observational test. We study a sample of hot white dwarf stars, combining far-UV spectroscopic observations, atomic physics, atmospheric modelling, and fundamental physics in the search for variation in the fine structure constant. This variation manifests as shifts in the observed wavelengths of absorption lines, such as quadruply ionized iron (FeV) and quadruply ionized nickel (NiV), when compared to laboratory wavelengths. Berengut et al. (Phys. Rev. Lett. 2013, 111, 010801) demonstrated the validity of such an analysis using high-resolution Space Telescope Imaging Spectrograph (STIS) spectra of G191-B2B. We have made three important improvements by: (a) using three new independent sets of laboratory wavelengths; (b) analysing a sample of objects; and (c) improving the methodology by incorporating robust techniques from previous studies towards quasars (the Many Multiplet method). A successful detection would be the first direct measurement of a gravitational field effect on a bare constant of nature. Here we describe our approach and present preliminary results from nine objects using both FeV and NiV.