Документ взят из кэша поисковой машины. Адрес оригинального документа : http://xmm.vilspa.esa.es/sas/6.5.0/doc/esrcselect.ps.gz Дата изменения: Tue Aug 16 04:12:46 2005 Дата индексирования: Tue Oct 2 08:33:19 2012 Кодировка: Поисковые слова: п п п п п п п п п п п п п п п п п п п п

XMM-Newton Science Analysis System Page: 1
esrcselect
August 16, 2005
Abstract
Select EPIC sources for product generation
1 Instruments/Modes
Instrument Mode
EPIC Imaging
2 Use
pipeline processing yes
interactive analysis no
3 Description
In the pipeline processing of XMM data, products will be created for individual sources detected in the
EPIC cameras. The source products (spectra and time-series) will only be produced for a selected number
of the detected sources (typically the brightest), and only in circumstances where the source products
can be generated reliably.
The task esrcselect will make the decision on which sources are candidates for source product gener-
ation. The task accepts two sources lists: the observation source list and the exposure source list. The
positions used to dene source and background regions are drawn from the exposure-level source list.
The source selection criteria may dier depending on whether a spectrum or a time-series is to be
produced, which is specied using the operationmode parameter. Currently there are no dierences in
the selection criteria, the operation mode merely denes which column in the observation source list will
be updated to re ect the production of products.
The conditions for the selection of a source are currently anticipated to be:
1. Distance from its nearest neighbour (from exposure source list) greater than a specied
threshold, to avoid producing products for confused sources
xmmsas 20050815 1803-6.5.0

XMM-Newton Science Analysis System Page: 2
2. Count rate (from observation source list) exceeding a specied minimum, to ensure good
statistics in a time-series
3. Count rate (from observation source list) not exceeding a specied maximum, to avoid
extracting products for piled-up sources
4. Number of source counts (from exposure source list) exceeding a specied minimum, to
ensure good statistics in a spectrum
Furthermore a limit can be placed on the number of sources selected. If the number of candidates would
otherwise exceed this limit, the brightest sources in the observation will be preferrentially selected.
Additional conditions may be necessary; these will be added as needed after in- ight experience has been
gained (see section 10).
For some instrument congurations (eg. observations including windowed or timing modes) sources in
the observation source list may not have a counterpart in the exposure source list. In such cases the
source will not be selected for source product generation.
The output from the task is a list of the selected sources, which is used as input to the task region. For
each select source the le lists the source ID number (from the observation source list) and the source
coordinates (from the exposure source list). The task also updates the observation source list, setting a
ag for each source which has been selected for product generation.
4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
obssourcelist yes table
Name of observation source list
expsourcelist yes table
Name of exposure source list
operationmode yes string spectrumjtimeseries
Mode of operation
minsourcerate yes real
Minimum source count rate (counts/sec, full EPIC band) of selected sources
maxsourcerate yes real
Maximum source count rate (counts/sec, full EPIC band) of selected sources
xmmsas 20050815 1803-6.5.0

XMM-Newton Science Analysis System Page: 3
minsourcecounts yes real
Minimum number of source counts (in full EPIC band) in selected sources
minsourceseperation yes real
Minimum distance from nearest neighbour (arcseconds) for selected sources
maxsources yes integer
Maximum number of sources in the selected list
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.
badInstrument (error)
INSTRUME keyword in exposure list is one of EMOS1, EMOS2 or EPN
setNotFound (error)
Exposure list supplied was not referenced during the creation of the observation list
6 Input Files
1. EPIC observation summary source list
2. EPIC exposure source list
7 Output Files
1. EPIC observation summary source list
2. List of selected sources. This le contains a table, called SRCLIST, with the following
columns:
Name Type Description
SRC NUM Integer Source ID from observation source list
RA Double RA from exposure source list
DEC Double Declination from expoure source list
RATE Real Count rate from observation source list
COUNTS Real Number of source counts, from exposure source list
DIST NN Real Nearest-neighbour distance from observation source list
xmmsas\_20050815\_1803-6.5.0

XMM-Newton Science Analysis System Page: 4
8 Algorithm
Read observation source list
Sort into order of descending count rate
Read names of exposure lists used to create observation list
from keywords in observation list
Check that supplied exposure list was used to create observation list
Read exposure source list
Find index into ML_ID_SRC vector columns for the given exposure list
while (source count rate > threshold && selected sources < maximum)
Check nearest neighbour threshold
Locate source in exposure source list
Check source counts against threshold
Check source count rate against threshold
Add source to selected list if all checks passed
end while
Write selected list
The correspondence between sources in the observation source list and the detections in the exposure list
is determined as follows:
 The observation source list contains a set of keywords M1 SET1, M1 SET2, M1 SETn, ...,
M2 SET1, M2 SET2, ..., dening the names of the exposure lists which were used to create
it.
 The observation source list contains columns M1 ML ID SRC, M2 ML ID SRC and PN ML ID SRC
which are vector columns. The nth element of the vector denes the value of ML ID SRC
in the nth for the detection of that source in the exposure list for that instrument.
9 Comments
10 Future developments
Further enhancements may be necessary in the light of in- ight experience, eg.
 location of the source within the camera eld-of-view, to avoid CCD boundaries)
 the nearest-neighbour distance threshold may need to be a function of source brightness, to
alleviate problems with multiple detection of bright sources (this depends on the performance
of the source detection software)
xmmsas 20050815 1803-6.5.0

XMM-Newton Science Analysis System Page: 5
References
xmmsas 20050815 1803-6.5.0