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XMM-Newton Science Analysis System


dpssflag (dpssflag-7.0.2) [xmmsas_20060628_1801-7.0.0]

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Description

The aim of this task is to flag sources in EPIC combined source list in an automatic way for later purification through visual screening.

The flags for each source are written back to the input source list using the column named ``FLAG''. The final flag string is a list of T/F characters, T in the position where the corresponding flag is set and F otherwise. The initial flag string is thus ``FFFFFFFFFF''.

Those sources with SCTS=NULL are not flagged.

The list of flags set by the task is as follows:

1. Flag 1: All those sources with a MASKFRAC column value lower than the value given by parameter mfraclimit will have their first flag set to true, i.e. from 'FFFFFFFFF' to 'TFFFFFFFF'. Flag 1 is propagated to the summary row (ID_INST=0) if it is set for any of the rows (ID_INST/ID_BAND) of that source.

2. Flag 2: The task defines a 'circle of influence' around each point source (whose parameters - position, count rate, etc.- are taken from its summary row). Then all neighbour sources (in every band and in every instrument) inside this circle will have flag 2 set to T, i.e. from 'FFFFFFFFF' to 'FTFFFFFFF'.

   The circle radius (in arcs) is calculated using task input parameters brcolumn,op1, op2 and brfactor as follows:

   
   

   op1	op2	Expression
   sqrt	add	sqrt(brcolumn(i)) + brfactor
   sqrt	mul	sqrt(brcolumn(i)) * brfactor
   sqrt	none	sqrt(brcolumn(i))
   none	add	brcolumn(i) + brfactor
   none	mul	brcolumn(i) * brfactor
   none	none	brcolumn(i)

   
   

   This 'circle of influence' will have a minimun and a maximum value given by the input parameters minrad and maxrad.

3. Flag 3: Using the information given in column EXT and the parameter extfactor the task defines a 'circle of extended emission' around each extended source. Then all sources (in every band and in every instrument) inside this circle will have flag 3 set, i.e. from 'FFFFFFFFF' to 'FFTFFFFFF'. The circle radius (in pixels) is calculated as :

   radius(i) = EXT(i) * extfactor
   

   Note: This radius is internally converted to arcs taking into account the pixel size of the images used for the source detection.

   This 'circle of extended emission' will have a maximum value in arcs given by the input parameter maxextrad.

   The starting value for a source being considered an extended source is controlled by parameter extlimit. Therefore those sources whith EXT value lower than extlimit will not be considered as 'extended' and will not define an area of extended emission.

4. Flag 4: likely spurious extended source in 'circle of influence' of bright point source. This flag will be set if source is extended (EXT$\geq$ extlimit), has Flag 2 set to true (i.e. is in circle of influence of a bright point source) and the causing source is brighter than counts given by parameter brlimit, i.e.:

   SCTS(causing_src) > brlimit
   

   Distance is calculated using information in the first ID_BAND=0 row and then propagated to the other ocurrences of that source.

5. Flag 5: likely spurious extended source inside 'fixed radius circle' of brighter extended source. This flag will be set if source is extended (EXT$\geq$ extlimit), is closer than a given distance (fixext) to another extended source and it has less than an input fraction (parameter brexfraction) of the causing source brightness (calculated from brcolumn), i.e.:

   brcolumn(src_flagged) < brexfraction * brcolumn(causing_src)
   

   Distance is calculated using information in the first ID_BAND=0 row and then propagated to the other ocurrences of that source.

6. Flag 6: likely spurious extended source: detection in one band. This flag will be set if source is extended (EXT$\geq$ extlimit) and has been detected in just one instrument, just one band, i.e. in just one of the 15 images:

   DET_ML(i,one_of_15_images) > detmlfraction * det_ml_sum(1:15)(i)
   

7. Flag 7: likely spurious extended source: it has Flag4, Flag5 or Flag6 set to ``T''.

8. Flag 8: The PN band 1 sources on a bad PN band 1 column (currently hardcoded, M.Freyberg communication) or those from MOS1 bands 1,2,3 on CCD 1 bad areas (J.Ballet communication) will have flag 8 set to T, i.e. from 'FFFFFFFFF' to 'FTFFFFFTF'.

9. Flag 9: Taking into account information from column given by parameter badcolumn (default CUTRAD) modified by parameter badfactor the task defines a 'distance to bad area' for the PN band 1 or the MOS1 CCD 1 bands 1,2,3. Then all sources closer than this distance to these bad areas (not on the bad areas) will have flag 9 set to T, i.e. from 'FFFFFFFFF' to 'FTFFFFFFT'. This 'critical' distance (in image pixels) is calculated as:

   distance(i) = badcolum(i) * badfactor
   

   Flag 9 for PN camera is switched off by default (see parameter pnclosetobadon).

   The activation of Flags 8 and 9 in PN band 1 or MOS1 CCD 1 bands 1,2,3 sources also sets these flags to 'T' for summary rows (ID_INST=0 and ID_BAND=0).