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XMM-Newton Science Analysis System Page: 1
emask
June 28, 2006
Abstract
Creation of detection mask (from exposure images), marking the area on which
source searching will be performed.
1 Instruments/Modes
Instrument Mode
EPIC MOS: IMAGING
EPIC PN: IMAGING
2 Use
pipeline processing yes
interactive analysis yes
3 Description
Using an exposure image from any of the EPIC instruments, a mask image representing the area on the
sky which is searched by the source detection tasks is constructed. Optionally circular regions read from
a ts region le are excluded from the mask. The region le must contain columns SHAPE, X, Y, and R
in the extension REGION. This format is provided by the SAS task ds9tocxc, the coordinates in X, Y
must be image pixels. The detection mask is a FITS image containing the integer values 0 and 1 where
1 marks the image area on which source searching will be performed.
4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
expimageset yes lename expimage.ts
Names of exposure image
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detmaskset yes lename detmask.ts
Name of detection mask
threshold1 no oat 0.3 [0.0 Threshold parameter 1: fraction of maximum exposure
threshold2 no oat 0.5 [0.0 Threshold parameter 2: threshold for gradient of exposure
withregionset no binary false
Read a ts region le and exclude circular regions
regionset no lename region.ts
Fits region le containing cirular regions
5 Errors
This section documents warnings and errors generated by this task (if any). Note that warnings and
errors can also be generated in the SAS infrastructure libraries, in which case they would not be docu-
mented here. Refer to the index of all errors and warnings available in the HTML version of the SAS
documentation.
Exposure images from dierent instruments have dierent pixel sizes, image sizes, center
coordinates (RA, Dec), or north vectors (not yet implemented) (fatal)
ColumnNotFound (warning)
Column X, Y, R or SHAPE missing in region ts le
corrective action: Ignore region le
WrongShape (warning)
Entry SHAPE in region le is not CIRCLE
corrective action: Ignore entry in region le
6 Input Files
1. PPS product (from task EEXPMAP): EPIC exposure image
7 Output Files
1. Detection mask (to be used by tasks EBOXDETECT, ESPLINEMAP, ESENSMAP) The
detection mask is a FITS image with the same binning as the EPIC FITS images containing
the integer values 0 or 1.
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8 Algorithm
Begin subroutine emask
Determine maximum of exposure
Multiply threshold parameters with exposure maximum
Optionally read region file
Loop over image pixels
Set pixels of detection mask to 1 if exposure is above cutoff
and 0 otherwise.
Set pixels inside circular regions to 0.
END Loop
Loop over image pixels
Set pixels of detection mask to 0 if gradient of exposure
is above threshold
END Loop
End subroutine emask
9 Comments
10 Future developments
 Add error handling and verbosity control.
 Add capability to operate on multiple exposure maps (see developer notes).
References
xmmsas 20060628 1801-7.0.0