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Поисковые слова: m 31

   
*imcnts* - Radial Profile of an extended source at the field center

Obtain a radial distribution of counts for the source centered at x = 503, y = 513, in the data image xdata$snr.qp. The background is taken locally from an annulus outside the source region. Errors are evaluated from the counts in the image and include the error on the background counts.

input file: xdata$snr.qp

output file: snr_cnt.tab

  cl> xray                     # Load the relevant packages (unless already loaded) 
  xr> xspatial 
  xs> imcnts                                                         # Run the task 
  source image file :  xdata$snr                          # xdata$snr.qp; make sure
            # there is no xdata$snr.imh file, or give the *.qp extension explicitly

   source region descriptor: a 503 513 0 50 n=5³

                 # 5 annuli at 503,513, 0 to 50 pixel min/max radii, 10 pixel width 
  background image file or cts/pixel :   ``''                 # blank filename will 
                                          # force the task to use the same filename 
  bkgd region descriptor:  a 503 513 100 150         # Annulus centered at 503,513, 
                                               # 100 to 150 pixel inner/outer radii 
  root name for output file [root\_cnt.tab]: snr                      # snr_cnt.tab

Region descriptors can also be given on the command line, but they must be enclosed by quotes.

  xs> imcnts xdata$snr ``a 503 513 0 50 n=5''

Either commas or spaces can be used to separate the parameters needed for a region.

The output tables can be read/printed with the stsdas-ttools package tasks

N.B.: The region specifications are identified with letters in the table headers, and the resulting regions are identified with numbers in the data section. There might not be a one to one correspondence between specifications in the header and regions in the data section. For example, when annuli are specified, as in the example above, there is only one specification in the header, but there are 5 regions in the table. For some regions (annuli and pie slices), the beginning and ending radii or angles are entered in the table.

Note also that the number of region specifications in the header is limited by the number of ASCII characters available. If the number of specifications is larger, the table will contain the total number of rows and the correct results, but the header information will be unreliable.