A GIANO-TNG high-resolution infrared spectrum of the airglow emission^⋆

¹ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
e-mail: oliva@arcetri.inaf.it
² INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
³ Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Avenue, Cambridge CB3 0HE, UK
⁴ INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁵ INAF – Fundación Galileo Galilei, Rambla José Ana Fernández Pérez, 7, 38712 Breña Baja, TF, Spain
⁶ Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Università di Catania, via S. Sofia 78, 95123 Catania, Italy
⁷ Lawrence Berkeley National Laboratory, MS 2-400, One Cyclotron Road, Berkeley, CA 94720, USA
⁸ Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁹ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei Muenchen, Germany

Received: 26 February 2013
Accepted: 11 May 2013

Abstract

Aims. A flux-calibrated high-resolution spectrum of the airglow emission is a practical λ-calibration reference for astronomical spectral observations. It is also useful for constraining the molecular parameters of the OH molecule and the physical conditions in the upper mesosphere.

Methods. We used the data collected during the first technical commissioning of the GIANO spectrograph at the Telescopio Nazionale Galileo (TNG). The high-resolution (R ≃ 50   000) spectrum simultaneously covers the 0.95–2.4 μm wavelength range. Relative flux calibration is achieved by the simultaneous observation of a spectrophotometric standard star.

Results. We derived a list of improved positions and intensities of OH infrared lines. The list includes Λ-split doublets, many of which are spectrally resolved. Compared with previous works, the new results correct errors in the wavelengths of the Q-branch transitions. The relative fluxes of OH lines from different vibrational bands show remarkable deviations from theoretical predictions: the Δv = 3, 4 lines are a factor of 2 and 4 brighter than expected. We also found evidence of a significant fraction (1–4%) of OH molecules with a non-thermal population of high-J levels. Finally, we list wavelengths and fluxes of 153 lines not attributable to OH. Most of these can be associated with O₂, while 37 lines in the H band are not identified. The O₂ and unidentified lines in the H band account for ≃5% of the total airglow flux in this band.