Description

The RMF used to analyze a source depends on what part of the chip the source falls on. As described in the mkrmf help page ("ahelp mkrmf"), the RMF is calculated using information stored in a FEF file. Since the information in the FEFs changes over the chip - the exact regions over which a particular FEF is valid depend on the chip and the focal-plane temperature - it is sometimes useful to see how the source photons are distributed with respect to this grid (this is particularly true for extended sources).

The regions.sl script provides a S-Lang function (display_fef_regions()) which requires an event file containing the source photons; it will accept the DM virtual-file syntax for filtering on-the-fly. The input file should only contain photons falling on a single ACIS chip, so it will be necessary to include a filter such as "ccd_id=<number>" if the source region covers more than one chip. It should also contain a TIME column, as the first entry is used to find out the focal plane temperature at the time of the observation.

The script is run from within ChIPS ("ahelp chips"), as shown in the example, or Sherpa ("ahelp sherpa"). To load the script:

chips> () = evalfile( "regions.sl" )

This step is only necessary once per ChIPS or Sherpa session.

This script is used in the Displaying the FEF Regions Covered by a Source thread.