SOAR TripleSpec

Overview

This file summarizes several instrument specific settings that are related to the SOAR/TripleSpec spectrograph (PypeIt name soar_tspec).

TripleSpec is a fixed-format, cross-dispersed near-infrared spectrograph. PypeIt reduces it with the Echelle pipeline, covering five orders (order numbers 7 through 3) spanning roughly 0.8–2.47 microns (\(\sim\)8000–24700 Angstrom, i.e. the z/J/H/K range). Because the format is fixed, the order positions, order numbers, and approximate spectral ranges are hard-coded in the spectrograph class.

PypeIt File

Here is some advice on how to setup your PypeIt Reduction File. First, run:

pypeit_setup -r absolute_path -s soar_tspec -b -c A

where -b indicates that the data use sky subtraction and the calib, comb_id, and bkg_id columns are added to the Data Block. See pypeit_setup and A-B image differencing for the syntax used for the data in these columns and how PypeIt uses them.

Here is an example of the Data Block of the PypeIt file:

# Data block
data read
 path ./
                                filename |       frametype | ... |  dispname |  decker | binning | exptime | calib | comb_id | bkg_id
         SPEC_DFLAT_04-02-2025_0088.fits |            dark | ... |      spec | default |     1,1 |     2.0 |     0 |      -1 |     -1
         SPEC_DFLAT_04-02-2025_0042.fits | pixelflat,trace | ... |      spec | default |     1,1 |     2.0 |     0 |      -1 |     -1
        SPEC_2025cy_05-02-2025_0116.fits | arc,tilt,science | ... |     spec | default |     1,1 |   300.0 |     0 |       1 |     -1
        SPEC_2025cy_05-02-2025_0117.fits | arc,tilt,science | ... |     spec | default |     1,1 |   300.0 |     0 |       2 |     -1
SPEC_2025cy_05-02-2025_standard0120.fits |        standard | ... | spec | default |     1,1 |    9.25 |     0 |       3 |     -1
data end

frametype is automatically assigned to each frame using the values of various header keywords (see check_frame_type()): the dome flats taken with the lamp on are typed pixelflat,trace, the dome flats taken with the lamp off are typed dark, and the science exposures are typed science.

Calibrations

Wavelength Calibration

TripleSpec has no dedicated arc lamp that is useful across the full near-IR range; instead, the dense forest of OH sky-emission lines in the science frames is used as the wavelength reference. You must therefore add the arc and tilt frame types to the science frames in the PypeIt file, as shown in the data block above, and comment out (or omit) any short dedicated arc exposures. The long (e.g. 300 s) science exposures contain far more usable OH lines than a short arc and give a much better solution, especially in the reddest order.

PypeIt ships a native reidentification archive, soar_triplespec.fits, that covers all five orders. The default parameters (set in default_pypeit_par()) use it via the reidentify method with the OH_NIRES line list, which carries OH lines all the way out to \(\sim\)24980 Angstrom and so anchors the reddest order (order 3, K band) with real lines. No user intervention is normally required.

Warning

If you change the frame typing (for example, switching which frames are used as the arc), you must delete the affected files in ``Calibrations/`` before re-running. run_pypeit -o overwrites only the science products, not the cached calibration frames, so a stale Arc_* / WaveCalib_* will silently be reused.

Flat Fielding

Dome flats are taken in pairs: lamp on and lamp off. PypeIt types the lamp-on flats as pixelflat,trace and the lamp-off flats as dark; the dark is subtracted to remove the thermal/dome background before the field flat and order edges are constructed. Bias subtraction and overscan correction are turned off for this detector.

Additional Reading

Here are additional docs relevant to reducing SOAR/TripleSpec data: