Jonathan Whitmore (Swinburne University of Technology)

The Fine-Structure "Constant" and VLT-UVES and Keck-HIRES wavelength calibration - Jonathan Whitmore Colloquium

ATNF Marsfield Lecture Theatre

Abstract

Measurements of a possible change in the fine-structure constant (alpha) are taken by comparing the atomic transition absorption features in quasar absorption spectra. A recent publication claims evidence of a spatial dipole (alpha larger in one direction, smaller in the other). The signal for this measurement comes entirely from very small (~100 m/s) relative velocity shifts between the atomic transitions. This means that precise wavelength calibration is crucial to these measurements. We present several unexpected wavelength miscalibrations of VLT-UVES and Keck-HIRES that may directly impact these measurements.