The Low-Redux Page

Brought to you by:

Joe Hennawi (UC Berkeley)
Scott Burles (MIT)
David Schlegel (LBL)
Jason X. Prochaska (UCO/Lick Observatory)

The core routines in this package have been developed to reduce longslit and multi-slit data from several, optical spectrometers on the Keck, Gemini, MMT, and Lick telescopes. The routines were initially developed for observations of faint point sources (quasars) but have been tested on bright point sources and relatively bright galaxies.

Quick Links

Low-Redux (XIDL) Install

Lick/KAST cookbook

Keck/LRIS cookbook

Keck/LRIS pixel flats

Low-Redux QA Examples

Low-Redux Version Notes




I. Overview of the Code

The code was developed in the spirit of algorithms developed for the SDSS spectral pipeline, the DEIMOS spectral pipeline, and the echelle pipelines developed for the MIKE and HIRES spectrometers. Unlike many of these other codes, the routines here are meant to form a nearly black-box pipeline. This is especially true for longslit reductions.
The general approach of the code is as follows:
  1. Examine the set of data files to determine image type.
  2. User then edits the 'plan' file.
  3. All of the following steps occur within one routine
    • Process the flats and trace the orders
    • Process the arcs and create 2D wavelength solutions
    • Create a slit profile
    • Process the object frames (flatten, CR reject)
    • Identify and trace the objects in the slit
    • Sky subtract
    • Extract
    • Correct for flexure using sky lines
  4. Coadd multiple exposures
  5. Create a sensitivity function from a standard
  6. Flux

II. Installing the Software

The code relies on several IDL packages in addition the routines specific to this pipeline.
  • The SDSS codes (both IDLUTILS and idlspec2d),
  • The XIDL package built by JXP.

More detailed notes for obtaining and installing these packages can be found here: install notes. We wish to emphasize that the code expects the most up-to-date versions of the Sloan codes. Users with old versions of any of these packages beware!

III. Instrument Supported

Beta Quality (best)

  • Lick/KAST Spectrometer
    • Blue side: G1, G2, G3 grisms
    • Red side: 600/5000, 600/7600, 300/7500,1200/5000 gratings
  • MMT/BCS Spectrometer
    • 800 grism
    • 831/3600 grism
    • 831/3900 grism
    • 300 GPM
  • Keck/LRIS Spectrometer
    • Both longslit and mutli-slit modes are supported
    • Blue side (longslit): 300/5000, 600/4000, 1200/3400 grisms
    • Blue side (multi-slit): 300/5000, 600/4000, 1200/3400 grisms
    • Red side: All gratings both multi-slit and long-slit
  • Gemini/GMOS Spectrometer
    • B600, R150, R831, R400
    • Includes multi-slit
Additional instruments (less supported):
  • Keck/DEIMOS Longslit
  • MMT/RCS
  • CAHA
  • Keck/NIRSPEC
  • Gemini/NIRI, GNIRS
If you have a longslit spectrum you wish reduced which is not included in the above lists, contact JH or JXP. Odds are we can add it to the package in quick fashion. Multi-slit is more challenging, but will also be considered.

IV. Developing the Code + Bug Fixing

We do encourage all users to consider ways to improve the code and to suggest them to us. Of course, we'd also like to hear about bugs. Please do make an effort to verify it is a bug in the code as opposed to 'user error'. Along those lines, if you are a novice to IDL, we suspect you will have many more 'user errors' than bugs to find.
This research is supported, in part, by NSF grant AST 03-07408.
last modified May/2007