Correcting METIS spectra for telluric absorption to maximize spectral fidelity

TL;DR

This paper discusses methods to correct telluric absorption in METIS mid-infrared spectra, aiming to improve spectral fidelity by addressing resolution variations across the instrument's field of view.

Contribution

It introduces techniques using synthetic telluric models to enhance correction accuracy for the high-resolution integral field spectrograph of METIS.

Findings

Synthetic telluric models improve correction accuracy.

Resolution variation impacts telluric correction procedures.

Methods enhance spectral fidelity in mid-IR observations.

Abstract

METIS is a mid-infrared instrument proposed for the European Extremely Large Telescope (E-ELT). It is designed to provide imaging and spectroscopic capabilities in the 3 - 14 micron region up to a spectral resolution of 100000. One of the novel concepts of METIS is that of a high-resolution integral field spectrograph (IFS) for a diffraction-limited mid-IR instrument. While this concept has many scientific and operational advantages over a long-slit spectrograph, one drawback is that the spectral resolution changes over the field of view. This has an impact on the procedures to correct for telluric absorption lines imprinted on the science spectra. They are a major obstacle in the quest to maximize spectral fidelity, the ability to distinguish a weak spectral feature from the continuum. The classical technique of division by a standard star spectrum, observed in a single IFS spaxel, cannot simply be applied to all spaxels, because the spectral resolution changes from spaxel to spaxel. Here we present and discuss possible techniques of telluric line correction of METIS IFS spectra, including the application of synthetic model spectra of telluric transmission, to maximize spectral fidelity.