Spatial variation in the fine-structure constant -- new results from VLT/UVES
Julian A. King, John K. Webb, Michael T. Murphy, Victor V. Flambaum, Robert F. Carswell, Matthew B. Bainbridge, Michael R. Wilczynska, F. Elliot Koch
备注：
47 pages, 35 figures. Accepted for publication by Monthly Notices of the Royal Astronomical Society. Please see http://astronomy.swin.edu.au/~mmurphy/pub.html for an ASCII version of table A1 and the full set of Voigt profile fits for appendix C
(abridged) We present a new analysis of a large sample of quasar absorption-line spectra obtained using UVES (the Ultraviolet and Visual Echelle Spectrograph) on the VLT (Very Large Telescope) in Chile. In the VLT sample (154 absorbers), we find evidence that alpha increases with increasing cosmological distance from Earth. However, as previously shown, the Keck sample (141 absorbers) provided evidence for a smaller alpha in the distant absorption clouds. Upon combining the samples an apparent variation of alpha across the sky emerges which is well represented by an angular dipole model pointing in the direction RA=(17.3 +/- 1.0) hr, dec. = (-61 +/- 10) deg, with amplitude (0.97 +0.22/-0.20) x 10^(-5). The dipole model is required at the 4.1 sigma statistical significance level over a simple monopole model where alpha is the same across the sky (but possibly different to the current laboratory value). The data sets reveal a number of remarkable consistencies: various data cuts are consistent and there is consistency in the overlap region of the Keck and VLT samples. Assuming a dipole-only (i.e. no-monopole) model whose amplitude grows proportionally with `lookback-time distance' (r=ct, where t is the lookback time), the amplitude is (1.1 +/- 0.2) x 10^(-6) GLyr^(-1) and the model is significant at the 4.2 sigma confidence level over the null model [Delta alpha]/alpha = 0). We apply robustness checks and demonstrate that the dipole effect does not originate from a small subset of the absorbers or spectra. We present an analysis of systematic effects, and are unable to identify any single systematic effect which can emulate the observed variation in alpha.
Rapid-response mode VLT/UVES spectroscopy of super iron-rich gas exposed to GRB 080310. Evidence of ionization in action and episodic star formation in the host
VLT/UVES observations of extremely strong intervening damped Lyman-alpha systems: Molecular hydrogen and excited carbon, oxygen and silicon at log N(HI)=22.4
Impact of instrumental systematic errors on fine-structure constant measurements with quasar spectra
我们提出了一种新的“超校准”技术测量高分辨率光谱仪的波长尺度的系统失真。通过将“太阳双星”或小行星的光谱与参考实验室太阳光谱进行比较，可以在整个光学波长范围内，在两个中阶梯光栅级（$\sim$ 50- 100埃）和整个摄谱仪臂（$\sim$ 1000- 3000埃）的尺度上，以$\sim$ 10 m s $^{-1}$的精度跟踪标准钍-氩校准中的失真。使用档案光谱从过去的20年中，我们探讨了超校准的历史VLT-UVES和凯克-HIRES摄谱仪。我们发现，系统误差在他们的波长尺度是无处不在的和大量的，与通常的$\pm$ 200 m s $^{-1}$每1000 μ m之间变化的远程失真。我们应用一个简单的模型，这些扭曲模拟光谱的特点大UVES和HIRES类星体样品，以前表明可能的证据，宇宙学的变化，精细结构常数，$α$。在$α$的虚假偏差产生的模型密切匹配的重要方面的VLT-UVES类星体的结果在所有的红移和部分解释HIRES的结果，虽然不是自洽在所有的红移。也就是说，扭曲的明显普遍性、大小和一般特征能够显著削弱类星体吸收线中$α$变化的证据。
