IRTF Data Reduction Resources

This page contains links to various resources for the reduction of data taken at the IRTF. We welcome contributions. For more information, contributions, or suggestions, please contact Adwin Boogert.

SpeX

Spectra taken in all observing modes of the pre-upgraded SpeX and the upgraded SpeX can be reduced with the well-tested, interactive program Spextool. The current version is 4.1 (version 5 is meant only for iSHELL, see below). It works in the IDL environment. All users should read Sections 1 and 2 of the manual (found in Spextool/manuals/) before attempting to run the software. A gzipped tar file uSpeXdata.tar.gz containing raw SXD+LXD_Long SpeX data can be used to test drive the downloaded Spextool package. Comments, suggestions for improvements, and bug reports should be directed to Mike Cushing at michael.cushing _at_ gmail _dot_ com.

iSHELL

iSHELL spectra can be reduced with version 5 of Spextool, which is only meant for iSHELL data reduction, not SpeX.

Download:
  • Spextool version 5.0.2 (released 12/Jun/2018; improved order location to account for the slight movement of the orders during grating changes)
  • K3 test data (optional; released 09/Oct/2017)
  • Lp3 test data (optional; released 09/Oct/2017)

Important release notes:

Spextool is an IDL-based data reduction package that was originally written to reduce SpeX data. With the release of version 5, iSHELL data can be reduced. This version *cannot* reduce SpeX data. The capability will be added soon. Until that time, SpeX users must continue to use v4.1 (see above) to reduce their data. SpeX users who use Spextool for the reduction of their data will find the new version familiar, but there are enough changes to the GUIs and code that we ask that all users read the manual (in Spextool/manuals/) to learn how to reduce iSHELL data. If the users wish to practice, they can download test data for the iSHELL configurations K3 and Lp3. One major difference between reduction of SpeX and iSHELL data is in the telluric correction process. A Vega model is used to remove the intrinsic spectral energy distribution of the A0 V standard star and the SpeX version of the code allows the user to adjust the equivalent widths of the hydrogen lines in the Vega model to match that of the A0 V standard star. However the wavelength range of iSHELL orders is so small that the hydrogen lines span at minimum two orders and thus the code cannot adjust the equivalent width of the hydrogen lines. Users should therefore be aware that there may be residuals in the final telluric-corrected spectra due to the mismatch in equivalent widths between the A0 V standard star and the Vega model. Finally, we note that a large amount of new code was required to make Spextool compatible with iSHELL. While we have done our best to beta test the code in all 16 observing modes, there will no doubt be bugs and problems until the code is put through its paces by users. Therefore please do not hesitate to contact both Mike Cushing (michael.cushing _at_ gmail _dot_ com) and Adwin Boogert (aboogert _at_ hawaii _dot_ edu) with any problems that might arise including anything that simply *seems* wrong. If you would like to be included on a mailing list to be notified when a new version is available, please email Mike and Adwin as well.


Atmospheric absorption correction using models:

We are developing software to correct atmospheric absorption in iSHELL spectra using models, eliminating or reducing the time needed for observing standard stars. A Beta version of the program Xtellcor_model is currently available. It uses models from the Planetary Spectrum Generator (PSG; Villanueva et al. 2018) that are accessed online, and thus the user does not need to compile atmospheric modeling software nor line lists on their local computer. The atmospheric models typically need to be optimized to the observing conditions by scaling the molecular columns, in particular that of H2O. Therefore, the method works best for studies of line to continuum ratios and if individual sky lines can be discerned. It performs less well for weak continuum targets with strong emission lines or if absolute flux calibration is required. When no standard stars are observed, the echelle order blaze shape is not divided out, and Xtellcor_model optionally allows for the flat fields to be used for that. This flat field method currently leaves curvature and slopes in the spectra affecting the analysis of science absorption or emission features that are broader than ~25% of an echelle order. Please note that this is a Beta release and not all iSHELL modes have been fully tested yet and observers should keep observing standard stars until they are comfortable with the quality of the atmospheric correction using models. We welcome feedback: Adwin Boogert (aboogert _at_ hawaii _dot_ edu) and Christian Flores Gonzalez (caflores _at_ hawaii _dot_ edu).

Xtellcor_model runs as part of the Spextool package, but currently must be installed separately using the tar file given below. Please follow the Cookbook in section 2 of the manual for installation and usage instructions. The tar file also includes test data:

MIRSI

Photometry with MIRSI data is described in mirsi_stepts.txt and these IDL library files are needed.

Apogee Camera

The data reduction for the (no longer offered) Apogee camera is described in apogee_steps.txt, and it requires these IDL library files.

Other Relevant Data Reduction Resources