An Image of Diffuse Emission

Overview

Synopsis:

The procedure used here is intended to make a nice image for a poster or paper and to aid in understanding the morphology of the extended emission. Point sources are identified and removed, filling the gaps with a sampling of the background region. The filled image is then smoothed, with the option to exposure-correct the results.

Care must be taken in the scientific interpretation of the final image as it is highly processed.

Purpose:

To create a smoothed image of diffuse emission, replacing point sources by a local estimate of the background emission.

Related Links:

• Analysis Guide: Extended Sources

• The File Format section of the Using CIAO Region Files: describes how to display region files on an event list, which is used often in this thread.

• Creating Source and Background Files: this method could be used to create the source and background region files as well.

Last Update: 08 Jul 2024 - Removed warning about early dataset.

Parameters for /home/username/cxcds_param/wavdetect.par


#
#   parameter file for wavdetect
#
#
#   input
#
        infile = broad_thresh.img Input file name
#
#   output
#
       outfile = sources.fits     Output source list file name
     scellfile = sources.scell    Output source cell image file name
     imagefile = sources.image    Output reconstructed image file name
   defnbkgfile = sources.nbkg     Output normalized background file name
#
#   scales
#
        scales = 2.0 4.0          wavelet scales (pixels)
#
#   end of wtransform parameters
#
########################################################################
########################################################################
#
#   wrecon parameters
#
#
#   PSF size parameters
#
       psffile = broad_thresh.psfmap Image of the size of the PSF
      (regfile = sources.reg)     ASCII regions output file
#
#   output options
#
      (clobber = no)              Overwrite existing outputs?
     (ellsigma = 4)               Size of output source ellipses (in sigmas)
     (interdir = ${ASCDS_WORK_PATH} -> /tmp) Directory for intermediate outputs
#
#########################################################################
#
#   wtransform parameters
#
#
#   optional input
#
     (bkginput = )                Input background file name
  (bkgerrinput = no)              Use bkginput[2] for background error
#
#   output info
#
  (outputinfix = )                Output filename infix
#
#   output content options
#
    (sigthresh = 1e-06)           Threshold significance for output source pixel list
 (bkgsigthresh = 0.001)           Threshold significance when estimating bkgd only
     (falsesrc = -1.0)            Allowed number of false sources per image
   (sigcalfile = ${ASCDS_CALIB}/wtsimresult.fits -> /soft/ciao/data/wtsimresult.fits) Significance calibration file
#
#   exposure info
#
      (exptime = 0)               Exposure time (if zero, estimate from map itself
      (expfile = )                Exposure map file name (blank=none)
    (expthresh = 0.1)             Minimum relative exposure needed in pixel to analyze it
#
#   background
#
      (bkgtime = 0)               Exposure time for input background file
#
#   iteration info
#
      (maxiter = 2)               Maximum number of source-cleansing iterations
     (iterstop = 0.0001)          Min frac of pix that must be cleansed to continue
#
#   end of wrecon parameters
#
########################################################################
#
#   run log verbosity and content
#
          (log = no)              Make a log file?
      (verbose = 0)               Log verbosity
#
#   mode  
#
         (mode = ql)         
    

Parameters for /home/username/cxcds_param/roi.par


        infile = sources_mod.fits Input src list
     fovregion =                  Input field of view region
  streakregion =                  Input streak region
    outsrcfile = sources/src%d.fits Output source list
    radiusmode = mul              Background radius computation method
     bkgradius = 3                Background radius
      num_srcs = 58               Number of sources output
        (group = group)           Make 1 srcregion per group or per individual source
    (targetbkg = all)             Make background around all sources or just target?
    (bkgfactor = 0.5)             Amount offset or multipled by src to be excluded by bkg
  (bkgfunction = add)             Add bkgfactor or multiply bkgfactor
       (maxpix = INDEF)           Maximum number of pixels when intersecting
       (fovres = 1)               Pixellation resulolution for fov check
    (streakres = 0.25)            Pixellation resulolution for streak check
(ignore_streaksrc = yes)             Ignore streak region for source list ?
      (evtfile = )                Event File (# counts per region)
      (clobber = no)              Remove existing output files?
      (verbose = 0)               tool verbosity
         (mode = ql)
    

Parameters for /home/username/cxcds_param/dmfilth.par


##
## DMFILTH --  fill in the hole
##
        infile = broad_thresh.img Input image file
       outfile = diffuse.img      Enter output file name
        method = POISSON          Interpolation method
       srclist = @exclude.src.reg List of sources to fill in
       bkglist = @exclude.bg.reg  List of background regions
     (randseed = 0)               Seed for random number generator
      (clobber = no)              OK to overwrite existing output file(s)?
      (verbose = 0)               Verbosity level
         (mode = ql)              
    

Parameters for /home/username/cxcds_param/aconvolve.par


#
# aconvolve.par file
#
#
        infile = diffuse.img      Input file name
       outfile = diffuse.sm.img   Output file name
    kernelspec = lib:gaus(2,5,1,7,7) Kernel specification
#
# auxillary outputs
#
  (writekernel = no)              Output kernel
   (kernelfile = ./.)             Output kernel file name
     (writefft = no)              Write fft outputs
      (fftroot = ./.)             Root name for FFT files
#
# processing parameters 
#
       (method = fft)             Convolution method
        (edges = wrap)            Edge treatment
        (const = 0)               Constant value to use at edges with edges=constant
          (pad = no)              Pad data axes to next power of 2^n
       (center = no)              Center FFT output
   (normkernel = area)            Normalize the kernel
#
# user specific comments
#
      (clobber = no)              Clobber existing output
      (verbose = 0)               Debug level
         (mode = ql)