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Spectroscopy

Basic characteristics of Michelle's spectroscopy modes

Michelle is capable of spectroscopy with R~100 - 30,000 in the 7 - 25 micron range as follows:

 

  • Low resolution long-slit spectroscopy (chop and nod)
    • R ~ 200 (with 2 pixel wide slit) at 7-14 microns
    • R ~ 110 (with 3 pixel wide slit) at 16-26 microns
  • Medium and high resolution long-slit spectroscopy (stare and nod)
    • R ~ 1000 with 2 pixel wide slit) at 7-26 microns
    • R ~ 3000 (with 2 pixel wide slit) at 7-26 microns
    • R ~ 10000-30000 (echelle, with 2-3 pixel wide slit) at 7-22 microns - with some limitations
  • Pixel dimension 0.183" (low-resolution); approx. 0.35" (echelle)
  • Slit length = 43.2" (note that current maximum chop throw is 15")
  • Slit widths = 0.366" to 1.304"; normally the 2 pixel wide (0.366") slit is used for point sources in the 10um region and the 3 pixel wide (0.549") slit is used in the 20um region; currently the 1-pixel slit cannot be used

 

As with other mid-IR imagers and low resolution spectrographs, accurate cancellation of the sky and telescope background is most readily achieved by the technique of chopping and nodding. Currently the maximum chop throw allowed on Gemini is 15 arcsec, which is considerably smaller than the Michelle field of view. Observations using Michelle's medium resolution gratings and the echelle are carried out in stare-nod mode, similar to the conventional near-IR technique (see the Mid-IR Resources pages for more information).