2016/06/30 by Matthew Bainbridge, Matthew B. Bainbridge, John K. Webb · 56 citations
Decision Sciences · Mathematics · Physics and Astronomy · #Algorithm #Astronomy and Astrophysical Research #Astrophysics #Computer science #Context (archaeology) #Fine-structure constant #Galaxy #Physics #Quasar #Redshift #Scientific Measurement and Uncertainty Evaluation #Spectral line #Statistical and numerical algorithms #astro-ph.IM
paper · pdf · doi:10.1093/mnras/stx179
published in Monthly Notices of the Royal Astronomical Society, stx179 (Oxford University Press) · 34 pages, 10 figures, 16 tables. Submitted to MNRAS
arxiv created 2017/01/19 · openalex publication_date 2017/01/21 · arxiv updated 2017/02/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 (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 zabs = 1.8389 absorber towards the zem = 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 (2011) and King et al (2012).