The objective of this post is to stimulate some discussion regarding one of the most critical spectroscopic data reduction steps: wavelength calibration.
Users are invited to share their experiences with GMOS data reduction and their use of the Gemini IRAF tasks (in the present case, GSWAVELENGTH and GSTRANSFORM). Answers to one or more of the questions below are very valuable.
1) Which wavelength range do you work on?
2) Do you employ the standard CuAr line list (the one that comes within the Gemini Package) or some edited line list (e.g., complemented from high-resolution spectra)? What is the impact of this on your data?
3) Do you run GSWAVELENGTH interactively? In the case of MOS, what fraction of the slits results in good/bad wavelength solutions and spectra rectifications?
4) What fit function (and order) do you usually employ to obtain the wavelength solution? Cubic splines? Chebyshev polynomials?
5) What tolerance (match parameter in GSWAVELENGTH task) is adequate for your data? What step in pixels (in the spatial direction) between each established coordinate function is adequate for good spectra rectifications?
6) What fit function and orders do you employ to map distortions along the spatial direction (parameters fitcxord and fitcyord of GSTRANSFORM task)?