IRAF Spectra



Resolution & Data Reduction M / Early L Dwarf
Sloan T-Dwarf Spectra Kirkpatrick Spectra

Resolution, Observing & Data Reduction

      R~300 was selected as a trade-off between providing enough resolution to detect spectral typing features, such as methane at 1.6 mm, between atmospheric OH lines, especially strong in the J and H bands, and keeping the resolution low enough to minimize integration times.

      CorMASS's raw spectra of faint objects are dominated by sky lines. To subtract this background, we subtract integrations of faint objects that were observed at two different slit positions. Taking care to subtract pairs that follow closely in time, we find this technique to be effective in reducing sky backgrounds.

Data Reduction utilizes both IRAF, centered on the APALL task for cross-dispersed echelle spectral extraction, and IDL, used for pre-processing and post-processing.

Back to top


M / Early L Dwarf

      L-dwarf classifications  to date have been carried out between 0.65mm and 1.0 mm, the red optical CCD wavelengths (Kirkpatrick  et al., 1999). CorMASS' simultaneous wavelength  coverage of 0.8 mm to 2.3 mm allows acess to not only important TiO,  CrH, FeH, and H2O features shortward of 1.0 mm, but  also to J-band FeH and K I features that  can also be used for spectral typing (Kirkpatrick et al.,  1994). CorMASS data will provide the foundation  for augmenting the current classification scheme with  these relatively brighter J-band features. 

Back to top


Sloan T-Dwarf Spectra

      The detection of Methane (CH4) at 1.6 mm and 2.2 mm is a telltale sign  that this Sloan object is a T-dwarf.  CorMASS' detection of the 1.6 mm  feature demonstrates this   instrument's ability to spectrally   identify identify these bonafide brown dwarfs. 

Back to top


Kirkpatrick Spectra

Compare our results with spectra from Kirkpatrick, J.D., et al, 1999, ApJ, 519, 802, figure 4:

Back to top