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Long Slit Spectra at High Resolution

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Grating/Camera configurations:

110 l/mm grating and long cameras

Resolving power:

~18,000 with 0.1 arcsec (2 pixel) slit in all but the M band, where R~13,000. Lower resolutions with wider slits

Typical uses:
(...and limitations)

(1) High resolution spectra with 49 arcsec long slit 

This mode provides the highest spectral resolution obtainable with GNIRS. Narrow slits are required to achieve high resolution and if AO is not used, slit losses are large. 

Wavelength coverage is about one-third of that with the long camera and the 32 l/mm grating (or the short camera and the 110 l/mm grating). Many grating settings would be required to cover an atmospheric window in this mode, with large overheads due to taking calibrations at each wavelength setting before moving the grating. Users thinking about this kind of observation are recommended to consider using the cross-dispersed mode instead.

Spectra of a K1 giant (BS6913) obtained at example grating settings are shown below, with central wavelengths 1.63um (4th order) and 2.22um (3rd order).


Example spectra:

Fig 1a: high-res long-slit spectrum in 4th order (H window, central wavelength 1.63um)
LB111 spectrum at 1.63um
Fig 1b: high-res long-slit spectrum in 3rd order (K-window, central wavelength 2.22um)
LB111 spectrum at 2.22um

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