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Spectroscopy

Basic characteristics of T-ReCS's spectroscopy modes

T-ReCS is capable of spectroscopy with R~100 - 1000 in the 8–26 micron range as follows:


  • Low resolution long-slit spectroscopy: R ~ 100 near 10 µm, R ~ 80 near 20 µm
  • Medium long-slit spectroscopy: R ~ 1000 near 10 µm
  • Pixel size in spatial direction = 0.09" (fixed)
  • Slit length = 21.6"
  • Slit widths = 0.21" to 1.32"
  • Low-Res Dispersion at 10 µm = 0.02213 µm/pix, delta lambda = 7.1 µm (entire N band) across detector
  • Low-Res Dispersion at 20 µm = 0.033 µm/pix, delta lambda = 10.6 µm (entire Q band)
  • Hi-Res Dispersion at 10 µm = 0.0019 µm/pix, delta lambda = 0.6 µm

The principal T-ReCS spectroscopy modes, plus the typical settings of five instrument components in each mode, are listed in the following table. (Note: l/D means wavelength/diameter of primary mirror.)


Mode Window Slit Width Filter Grating Detector
10 µm Lo-Res Spectroscopy ZnSe 10 µm l/D or 2l/D N 10 µm Lo-Res Low-background
20 µm Lo-Res Spectroscopy KRS-5 20 µm l/D or 2l/D Qbroad 20 µm Lo-Res Low-background
10 µm Hi-Res Spectroscopy ZnSe 10 µm l/D or 2l/D N 10 µm Hi-Res Low-background

Like 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 chopper throw allowed on Gemini is 15 arcsec, which is considerably smaller than the T-ReCS field of view.