The Spectrum of Th‐Ar Hollow Cathode Lamps in the 691–5804 nm region: Establishing Wavelength Standards for the Calibration of Infrared Spectrographs

Abstract

We report new observations of the infrared (IR) spectrum of low-current Th-Ar hollow cathode lamps with the 2 m Fourier transform spectrometer (FTS) at the National Institute of Standards and Technology. These observations establish more than 2400 lines that are suitable for use as wavelength standards in the range 900Y4500 nm. The line list is used as input for a physical instrument model that provides the wavelength calibration for the Cryogenic HighResolutionIREchelleSpectrometer(CRIRES),theEuropeanSouthernObservatory’snewhigh-resolution(R � 100;000) IRspectrographattheVeryLargeTelescope.Wehavealsoobservedthevariationof thespectrumof Th-Arlampsasa function of operating current. The results allow us to optimize the spectral output in terms of relative intensity and linedensityforoperationonthetelescope.OurresultsshouldbegenerallyusefulforwavelengthcalibrationinnearIR astronomy, providing a high density of sharp, well-characterized emission lines with the ease and efficiency of operation of a commercial discharge lamp. Subject headingg atomic data — catalogs — instrumentation: spectrographs — methods: laboratory — standards — techniques: spectroscopic