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: http://xmm.vilspa.esa.es/sas/7.0.0/documentation/threads/src_find_thread_stepbystep.html
Дата изменения: Tue Aug 22 17:29:37 2006 Дата индексирования: Sat Dec 22 15:18:28 2007 Кодировка: Поисковые слова: m 63 |
In this thread, we will assume that a user intends to detect sources on a single MOS image, extracted in the 0.2-10 keV band. The event list MOS.evt is assumed to have been already cleaned for high-background intervals, following, e.g., steps 3. to 5. in the edetect_chain thread.
evselect table=MOS.evt:EVENTS imagebinning='binSize' \
imageset='mos_image_full.fits' withimageset=yes xcolumn='X' ycolumn='Y' \
ximagebinsize=80 yimagebinsize=80 \
expression='#XMMEA_EM&&(PI in [200:10000])&&(PATTERN \
in [0:12])&& gti(mos_back_gti.fits,TIME)'
eexpmap attitudeset=AttHK.ds eventset=MOS.evt imageset=mos_image_full.fits \
expimageset=MOS_expmap.ds pimin="200" pimax=10000"
where AttHK.ds is the attitude history file (file *ATT*FIT in the PPS products). An example of exposure map is shown in Fig.1
Fig.1: Example of MOS exposure map
emask expimageset=MOS_expmap.ds threshold1=0.25 detmaskset=MOS_mask.ds
where threshold1 indicates the maximum exposure fraction for a masked pixel (see the emask parameters description). In this specific example all pixels whose exposure time is lower than 0.25 times the maximum exposure are given value "0" in the mask, and excluded from the area where the source detection is performed. Users may relax this choice after a careful look at the exposure map, if they want to seek sources on a larger area. An example of MOS mask is shown in Fig.2
Fig.2: Example of MOS mask
eboxdetect usemap=no likemin=8 withdetmask=yes detmasksets=MOS_mask.ds \
imagesets=mos_image_full.fits expimagesets=MOS_expmap.ds pimin=200 \
pimax=10000 boxlistset=eboxlist_local.fits
where likemin is the minimum detection likelihood (see the eboxdetect parameters description as well).
esplinemap bkgimageset=MOS_bkg.ds scut=0.005 imageset=mos_image_full.fits \
nsplinenodes=16 withdetmask=yes detmaskset=MOS_mask.ds withexpimage=yes \
expimageset=MOS_expmap.ds
where nsplinenodes is the number of nodes employed in the background
map interpolation and scut the source surface brightness level (in
counts per arcseconds squared), above which a source is masked
(see the esplinemap parameters description). Particular care needs
to be used in the choice of nsplinenodes. A small number of nodes
may fail to accurately reproduce the background spatial distribution; an
excessive number of nodes may create faked structures. The optimal
compromise depends on the spatial pattern of the X-ray emission
(background+sources) in a
given field of view. Users are encouraged to try different choices
for this parameter, and compare the resulting maps with the observed
background spatial distribution pattern. The parameter scut
mainly drives the amount of source contamination
to the interpolated background map, due to the broad wings of the
Point Spread Function. The best value of scut is determined by the optimal
balance between background integration area and acceptable
source contamination level. This is obviously dependent on the
amount of background and the on crowdedness of the field. Users are
encouraged to check the background maps produced by
esplinemap
for short-scale fluctuations, and tune the scut value accordingly.
An example of MOS background map is shown in Fig.3.
Fig.3: Example of MOS background map
eboxdetect usemap=yes bkgimagesets=MOS_bkg.ds likemin=8 withdetmask=yes \
detmaskset=MOS_mask.ds imagesets=mos_image_full.fits \
expimagesets=MOS_expmap.ds pimin=200 pimax=10000 boxlistset=eboxlist_map.fits
emldetect imagesets=mos_image_full.fits expimagesets=MOS_expmap.ds \
bkgimagesets=MOS_bkg.ds boxlistset=eboxlist_map.fits ecf=2.0 \
mllistset=emllist.fits mlmin=10 determineerrors=yes
esensmap expimagesets=MOS_expmap.ds bkgimagesets=MOS_bkg.ds \
detmasksets=MOS_mask.ds mlmin=10 sensimageset=MOS_sens_map.fits
i.e. a pixel-by-pixel detection upper limit map. An example of MOS sensitivity map is shown in Fig.4.
Fig.4: Example of MOS sensitivity map
srcdisplay boxlistset=emllist.fits imageset=mos_image_full.fits sourceradius=0.01