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

R. I. Thompson, J. Bechtold, J. H. Black, C. J. A. P. Martins

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 μ = 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 3×10−7 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.

New Astronomy
Volume 14, Page 379
2009 May

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa Fundação para a Ciência e a Tecnologia
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