Molecfit: A general tool for telluric absorption correction - II. Quantitative evaluation on ESO-VLT/X-Shooterspectra
By W. Kausch, S. Noll, A. Smette, Stefan Kimeswenger, M. Barden, C. Szyszka, A. Jones, H. Sana, H. Horst, F. Kerber. 2015
295 citations recorded by the source corpus.
Context. Absorption by molecules in the Earth’s atmosphere strongly affects ground-based astronomical observations. The resulting absorption line strength and shape depend on the highly variable physical state of the atmosphere, i.e. pressure, temperature, and mixing ratio of the different molecules involved. Usually, supplementary observations of so-called telluric standard stars (TSS) are needed to correct for this effect, which is expensive in terms of telescope time. We have developed the software package molecfit to provide synthetic transmission spectra based on parameters obtained by fitting narrow ranges of the observed spectra of scientific objects. These spectra are calculated by means of the radiative transfer code LBLRTM and an atmospheric model. In this way, the telluric absorption correction for suitable objects can be performed without any additional calibration observations of TSS. Aims. We evaluate the quality of the telluric absorption correction using molecfit with a set of archival ESO-VLT/X-Shooter visible and near-infrared spectra. Methods. Thanks to the wavelength coverage from the U to the K band, X-Shooter is well suited to investigate the quality of the telluric absorption correction with respect to the observing conditions, the instrumental set-up, input parameters of the code, the signal-to-noise of the input spectrum, and the atmospheric profiles. These investigations are based on two figures of merit, Ioff and Ires, that describe the systematic offsets and the remaining small-scale residuals of the corrections. We also compare the quality of the telluric absorption correction achieved with molecfit to the classical method based on a telluric standard star. Results. The evaluation of the telluric correction with molecfit shows a convincing removal of atmospheric absorption features. The comparison with the classical method reveals that molecfit performs better because it is not prone to the bad continuum reconstruction, noise, and intrinsic spectral features introduced by the telluric standard star. Conclusions. Fitted synthetic transmission spectra are an excellent alternative to the correction based on telluric standard stars. Moreover, molecfit offers wide flexibility for adaption to various instruments and observing sites.
Subfields: Atmospheric Science, Global and Planetary Change, Spectroscopy
View Paper: https://www.semanticscholar.org/paper/edb1d713480e9a751e888f62e84369c562307bcd
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Citations in the corpus
- A Multimessenger Picture of the Flaring Blazar TXS 0506+056: Implications for High-energy Neutrino Emission and Cosmic-Ray Acceleration (2018, methodology): “The telluric absorption lines were removed by using the Molecfit software through a fit of synthetic transmission spectra calculated by a radiative transfer code (Kausch et al. 2015; Smette et al. 2015).”
- Detection of the Far-infrared [O iii] and Dust Emission in a Galaxy at Redshift 8.312: Early Metal Enrichment in the Heart of the Reionization Era (2018, methodology): “Corrections for telluric absorption lines were applied from models with MOLECFIT (Kausch et al. 2015) applied to observations of hot stars following the science integrations.”
- The GALAH Survey: Second Data Release (2018, methodology): “After the sky spectrum is subtracted, a telluric absorption spectrum is calculated using Molecfit software (Kausch et al. 2015; Smette, A. et al. 2015) and the science spectra are corrected.”
- Discovery of extreme [O III] λ5007 Å outflows in high-redshift red quasars (2015, unknown): “Telluric corrections were performed using MOLECFIT (Kausch et al. 2015; Smette et al. 2015).”