Alternative Data Reduction Procedures for UVES: Wavelength Calibration and Spectrum Addition

TL;DR

This paper presents alternative wavelength calibration and spectrum addition procedures for UVES spectra, achieving higher wavelength precision crucial for studying fundamental constants in the early universe.

Contribution

It introduces a customized wavelength calibration method that improves precision by selecting specific calibration lines, applicable to UVES and other spectrometers.

Findings

Achieved relative wavelength precision better than 3E-7.

Enhanced calibration accuracy over standard pipeline methods.

Applicable to spectroscopic studies requiring extreme wavelength precision.

Abstract

This paper addresses alternative procedures to the ESO supplied pipeline procedures for the reduction of UVES spectra of two quasar spectra to determine the value of the fundamental constant mu = Mp/Me at early times in the universe. The procedures utilize intermediate product images and spectra produced by the pipeline with alternative wavelength calibration and spectrum addition methods. Spectroscopic studies that require extreme wavelength precision need customized wavelength calibration procedures beyond that usually supplied by the standard data reduction pipelines. An example of such studies is the measurement of the values of the fundamental constants at early times in the universe. This article describes a wavelength calibration procedure for the UV-Visual Echelle Spectrometer on the Very Large Telescope, however, it can be extended to other spectrometers as well. The procedure described here provides relative wavelength precision of better than 3E-7 for the long-slit Thorium-Argon calibration lamp exposures. The gain in precision over the pipeline wavelength calibration is almost entirely due to a more exclusive selection of Th/Ar calibration lines.