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Last modified: 26 October 2016

URL: http://cxc.harvard.edu/ciao/bugs/dmfilth.html

Bugs: dmfilth


Table of Contents

Caveats

Bugs


Caveats

ERROR: Could not allocate memory for 'output_pixels'.

A common error with dmfilth is to use an event file as input instead of an image. If an event file is used event file, the tool bins it into a very large image (8192 x 8192 for ACIS). With an image that large all the system memory can easily be exhausted -- especially if running on a 32bit machine which is limited to ~2Gb of memory per-application (regardless of how much memory is installed).

Ensure that an image is being used (dmlist the file will show either 'Table' or 'Image'). If using a table (ie event file) then it should be binned into an image first.


Bugs

When using POISSON method, the distribution varies from true Poisson distribution slightly.

This is only detectable with many (hundreds) of runs.

The DIST method assumes positive, integer counts  (15 Mar 2012)

The tool will fail if this method is used with exposure-corrected images or if there are negative pixels in the source or background regions.

unix% dmstat "events.fits[sky=region(source.reg)]"
EVENTS_IMAGE(x, y)
    min:        -2.0534541607         @:        ( 4620.5 4868.5 )
    max:        63.77072525           @:        ( 4588.5 4876.5 )
cntrd[log] :    ( 5.7060806841 5.973494067 )
cntrd[phys]:    ( 4586.1486455 4876.2879525 )
sigma_cntrd:    ( 6.3023091173 6.8273372496 )
   good:        70 
   null:        40 

Last modified: 26 October 2016
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