# EDM Tue Apr 19 13:30:05 EDT 2011

xis_scatter.sh shows an example of a script to estimate the PSF scatter for
Suzaku/XIS.  There are two ftools task run: "mkphlist" which produces an
incedent photon list based on a provided spatial/spectral source model; and
"xissim" which runs these photons through the telescope and instrument
ray-tracing to create an observed event list.  mkphlist and xissim have
extensive help files in ftools.

mkphlist notes:
- "fits_image_file" specifies an input FITS image (e.g. the very core or
  inner 3 arcmin from XMM or Chandra) to use as the source
- "qdp_spec_file" specifies a QDP spectrum (e.g. from "plot model" in
  XSPEC) to use as the input spectrum
- you can use the same output photon list for any detector xissim run, so
  even though you can run mkphlist as part of xissim (with
  "enable_photongen") it might be better to do it separately

xissim notes:
- this is the task that xissimarfgen is based on, it just outputs an event
  list instead of an ARF
- you can take the output event list and extract spectra from the regions
  that you want, and simply use this as a background in XSPEC; just make
  sure to scale the exposure time so that the flux is right, since the
  output number of events from xissim only depends on the input number of
  photons.  One way to do this is to specify the "photon_flux" in mkphlist
  to be what you get from the XMM data within the source region.
- you can also just use the output event list to estimate the photon or
  energy flux within your Suzaku annulus, to compare to the cluster at that
  point and see if it's a large fraction (again, make sure to scale it
  right)
- I have set "attitude=none" and used fixed Euler angles for the pointing,
  you can also specify the attitude file and let it figure out the pointing
- the "ptgs" array is for different Suzaku pointings; you probably just
  have one for each cluster
- some of the CALDB files I specify might be outdated, since this is from a
  couple years ago

Finally, it might be good to determine the scattering due to two different
sources: the bright core (for cool core sources) as well as a ~ 1 arcmin
wide annulus just inside and outside of the 3-6 arcmin annulus.  This last
part is especially true for clusters where the kT profile is steep in the
3-6 arcmin radius.  And perhaps you can do this for one or two clusters to
get a sense of how important it is before doing it for the full sample.