aXe Reduction Methodology in a Nutshell
The aXe reduction tasks enable automated, efficient extraction of thousands of spectra from slitless spectral images. The software drives the spectral extraction based on two sets of information:
- a catalogue of objects in the field, and
- configuration files which calibrate the positioning of the spectra and the wavelength dispersion solution, and convert from extracted detector units to physical flux units.
aXe is not instrument specific, and can accommodate data from different instrument/grism combinations by specifying the required parameters in the configuration file.
aXe is PyRAF/IRAF software which is comprised of several tasks and is distributed as a subpackage of the Space Telescope Data Analysis System (STSDAS) under analysis.slitless.axe. Download and installation instructions can be found at the STSDAS website. Detailed notes on aXe releases and bugs can be found here.
aXe was originally designed to support Multidrizzle style astrometric information. Current (aXe v2.3) and earlier versions of the software rely on output files from the Multidrizzle process to transform object pixel coordinates between the user supplied "drizzled" direct image and corresponding spectral images. We are currently working on updating aXe to accommodate the use of new Astrodrizzle products, and maintain back-compatability with Multidrizzle.
A version of aXe, where iolprep and fcubeprep has been modified for compatibility with Astrodrizzle, is available via SSBX (aka IRAFX, the STSDAS testing environment). Work and testing of these tasks are still on-going. Release notes can be found here.
- WFC3/IR Grism Cookbook – Short step-by-step guide to reducing G141 (IR) grism data using aXe. Includes link to download Grism data from the WFC3 ERS Program, which is used as an example in the guide.
- aXe User Manual – Provides detailed documentation on all tasks and parameter settings in aXe, including more sophisticated reduction options not discussed in the WFC3/IR Grism Cookbook.
- aXe PASP Paper – Overview of aXe methodology (Kummel et al. 2009).
- aXedrizzle Overview – Description of procedure for the co-addition of the 2D spectra. Not to be confused with Astrodrizzle which is for the co-addition of direct imaging data.