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XMM-Newton Science Analysis System Page: 1
esplinemap
January 10, 2003
Abstract
ESPLINEMAP uses the eboxdetect local mode source list to derive spline back-
ground maps from the non-source regions.
1 Instruments/Modes
Instrument Mode
EPIC MOS IMAGING
EPIC PN IMAGING
2 Use
pipeline processing yes
interactive analysis yes
3 Description
Sources found in the local detection step (task eboxdetect) at signicance levels (column SIGMA of
eboxdetect source list) exceeding a user-speciable threshold (input parameter mlmin) are removed from
the image using a suitable PSF and source brightness dependent cut-out radius (determined to be the
radius at which each source contributes more than a user-speciable number of counts/arcsec 2 to the
background; parameter scut; default value: 0.01). The resulting image can optionally be output for
diagnostic purposes. After the removel of the sources the image is rebinned, such that a signicant
background signal is achieved in each bin. Division of the image by the exposure image removes gradients
due to spatial variations of the exposure from the image which otherwise would not be well represented
by the spline t. A two dimensional spline t of the rebinned and exposure corrected image is performed.
The number of spline nodes (default value: 16) is user-selectable. Finally, the resulting spline image is
again multiplied by the exposure images. If pixels of the rebinned image deviate from the spline t by
more than a speciable number of sigmas (default value: 4 sigmas) the excesses are removed and the spline
t is repeated (maximum number of iterations may be specied). The reduced chi 2 and corresponding
number of degrees of freedom of the background map with respect to the input image is stored in the
keywords CHISQR and NDOF of the output background map.
From version 3.0 esplinemap is able to determine the background caused by out-of-time events registered
during the readout process of the PN CCDs. If the ag withootset is set, the photon event table specied
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in ooteventset is read and the background caused by OOT events is included in the output background
map. As input table esplinemap can use either a normal photon event data-set or a photon events table
created with epevents with ag withoutoftime set. Note that in both cases a photon event set has to
be ltered with the same temporal and ag selections as the image used as input to esplinemap.
4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
boxlistset yes lename eboxlist.ts
Name of eboxdetect source list
imageset yes lename image.ts
Names of input EPIC ts images
bkgimageset yes lename bkgimage.ts
Name of output spline background map
expimageset no lename expimage.ts
Name of input exposure map
detmaskset no lename detmask.ts
Name of input detection mask
scut no oat 0.01 [0.0  param  10.0]
Source cut-out ux level; [counts/arcsec 2 ]
idband no integer 1 [0  param  9]
Band id from eboxdetect source list
mlmin no oat 1.0 [0.0  param  50.0]
Minimum detection likelihood for sources to be cut out
nsplinenodes no integer 16 [10  param  20]
Number of spline nodes
excesssigma no oat 4.0 [1.0  param  6.0]
Threshold for excesses sigmas with respect to background spline t
ntrun no integer 3 [1  param  5]
Number of iterations for removal of excesses
withdetmask no boolean true
Flag to use detection mask
withexpimage no boolean true
Flag to use exposure map
withcheese no boolean false
Controls optional output of photon image where sources have been masked out (socalled cheesed image)
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withootset no boolean false
Flag to use event table to calculate background due to out-of-time events.
ooteventset no lename events.ts
Name of photon event table used for background due to out-time-events
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.
SplineFitError (error)
Less than 1 data point for chi**2
SplineFitError (error)
Error condition in spline t
SplineFitError (error)
Error in LPSROS
SplineFitError (error)
Error in CALBCS
SplineFitError (error)
Error in ERPLPS
6 Input Files
1. PPS product (from task eboxdetect run in local detect mode): EPIC eboxdetect local
mode source list
2. PPS product (from task evselect): EPIC FITS image
3. PPS product (from task eexpmap): EPIC exposure image
4. from task emask: Detection mask
5. Filtered photon event list from evselect.
7 Output Files
1. Spline background map (to be used by the tasks eboxdetect (map mode), taskemldetect,
and esensmap)
2. Photon image where sources have been removed (socalled cheesed image; optional diagnostic
output)
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8 Algorithm
subroutine esplinemap
1) If out-of-time events flag is set: Calculate background due to
OOT events and subtract from image.
2) Remove source count dependent circular area around EBOXDETECT
(local mode) sources
which have detection likelihoods greater than a specifiable
threshold from the image.
3) If exposure flag is set, divide image by exposure map.
4) Perform spline fit of image, using a user-specifiable
number of spline nodes. If detection mask flag is set,
only use image regions marked by detection mask.
5) If exposure flag is set, multiply spline image by exposure map.
6) IF rebinned image pixels contain excesses above spline fit
THEN
remove excesses from image and repeat (2) - (5) a specifiable
number of times
END IF
7) If out-of-time events flag is set: Add OOT events background to background map.
end subroutine esplinemap
9 Comments
10 Future developments
References
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