Revisiting the impact of atmospheric dispersion and differential refraction on widefield multiobject spectroscopic observations: From VLT/VIMOS to next generation instruments

Par Conseil national de recherches du Canada

DOI	Trouver le DOI : https://doi.org/10.1051/0004-6361/201423459
Auteur	Rechercher : Sánchez-Janssen, R.¹; Rechercher : Mieske, S.; Rechercher : Selman, F.; Rechercher : Bristow, P.; Rechercher : Hammersley, P.; Rechercher : Hilker, M.; Rechercher : Rejkuba, M.; Rechercher : Wolff, B.
Affiliation	Conseil national de recherches du Canada. Infrastructure scientifique nationale
Format	Texte, Article
Sujet	Atmospheric movements; Refraction; Scheduling; Surveys; Atmospheric dispersion; Atmospheric effects; Instrumentation: spectrographs; Methods:observational; Overall efficiency; Parallactic angle; Spectral distortions; Techniques: spectroscopic; Instruments
Résumé	Context. Atmospheric dispersion and field differential refraction impose severe constraints on widefield, multiobject spectroscopic (MOS) observations, where the two joint effects cannot be continuously corrected. Flux reduction and spectral distortions must then be minimised by a careful planning of the observations, which is especially true for instruments that use slits instead of fibres. This is the case of VIMOS at the VLT, where MOS observations have been restricted, since the start of operations, to a narrow two-hour range from the meridian to minimise slit losses, the so-called two-hour angle rule. Aims. We revisit in detail the impact of atmospheric effects on the quality of VIMOS-MOS spectra with the aim of enhancing the instrument's overall efficiency, and improving the scheduling of observations. Methods. We model slit losses across the entire VIMOS field of view as a function of target declination. We explore two different slit orientations at the meridian: along the parallactic angle (north-south), and perpendicular to it (east-west). Results. We show that, for fields culminating at zenith distances larger than 20 degrees, slit losses are minimised with slits oriented along the parallactic angle at the meridian. The two-hour angle rule holds for these observations using north-south orientations. Conversely, for fields with zenith angles smaller than 20 degress at culmination, losses are minimised with slits oriented perpendicular to the parallactic angle at the meridian; MOS observations can be effectively extended to plus/minus three hours from the meridian in these cases. In general, night-long observations of a single field will benefit from using the east-west orientation. All-sky or service mode observations, however, require a more elaborate planning that depends on the target declination, and the hour angle of the observations. Conclusions. We establish general rules for the alignment of slits in MOS observations that will increase target observability, enhance the efficiency of operations, and speed up the completion of programmes, a particularly relevant aspect for the forthcoming spectroscopic public surveys with VIMOS. Additionally, we briefly address the non-negligible impact of field differential refraction on future widefield MOS surveys. © ESO, 2014.
Date de publication	2014
Dans	Astronomy and Astrophysics 566, A2 (2014).
Langue	anglais
Publications évaluées par des pairs	Oui
Publication du CNRC	Cette publication n’est pas du CNRC Ce sont des publications qui ont été rédigées par un auteur du CNRC, mais avant que celui-ci soit employé du CNRC.
Numéro NPARC	21272317
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Identificateur de l’enregistrement	645a79a9-33d8-4359-91f3-7cbc55bb6f7c
Enregistrement créé	2014-07-28
Enregistrement modifié	2020-04-22

Date de modification :: 2024-06-29