Sky emission subtraction for observations without plain sky information: skycorr
In the red part of the optical and the near-IR, the sky background is dominated by highly variable airglow emission lines. This is an issue for the sky subtraction in spectra without plain sky, where reference sky spectra taken at a different time as the object spectrum are required. The instrument-independent sky subtraction code Skycorr uses physically motivated line group scaling in the reference sky spectrum by a fitting approach for an improved sky line removal in the object spectrum. Possible wavelength shifts between both spectra are corrected by fitting Chebyshev polynomials and advanced rebinning without resolution decrease. For the correction, the optimised sky line spectrum and the automatically separated sky continuum (without scaling) is subtracted from the input object spectrum.
Tests show that Skycorr performs well (per cent level residuals) for data in different wavelength regimes and of different resolution, even in the cases of relatively long time lags between the object and the reference sky spectrum. Lower quality results are mainly restricted to wavelengths not dominated by airglow lines or pseudo continua by unresolved strong emission bands.
The software releases here are fully compliant to ESO official releases. For dedicated subversion see our spin-off projects page.
Manuals
Skycorr User Manual
Publications
If you use the software it is highly desired that you cite the papers and give a footnote or acknowledgement ot the page http://www.uibk.ac.at/eso/software. Too keep track (also for our funding agency) it would be nice to receive reprints or ADS/arxiv links if you do so.
Skycorr: A general tool for spectroscopic sky subtraction
S. Noll, W. Kausch, S. Kimeswenger, M. Barden, A. M. Jones, A. Modigliani, C. Szyszka, and J. Taylor, 2014, A&A, 567, A25.
Download - Installation packages
The latest version of the installers:
GNU/Linux 32 bit x86
GNU/Linux 64 bit x86
MacOS 64 bit x86
The installers include example data and configurations for FORS, SINFONI and XSHOOTER instruments.
The installation procedure is described here.
Please contact the team for more details. See also the ESO web pages.