XMM-Newton Science Analysis System: User Guide

4.12.3 Source detection example

In the following section (§ 4.12.3.1) an example on how to perform EPIC source detection analysis calling in sequence the individual edetect_chain subtasks is shown. This gives detailed information about the detection process. If, however, the user is happy with the default parameter settings for a standard source detection session, he/she might skip this section and continue directly with § 4.12.3.2 where the source detection is performed in one go via the edetect_chain task.

In the following it is assumed that the user has created a calibrated EPIC event list (or uses one from the pipeline processing) and has cleaned it for high flaring background periods (see § 4.4.4 and analysis step 1 and 2 in § 4.12.2.1). The assumed name of this filtered event list is filtered.fits.

The user can make use of the pipeline produced images (IMAGE_1 to IMAGE_5, see Table 4). Alternatively, images in these or different energy bands need to be generated first with e.g. the following command (see also § 4.12.2.1, analysis step 3):

evselect table=filtered.fits withimageset=true imageset=image_b1.fits \
         xcolumn=X ycolumn=Y imagebinning=binSize ...\

in case of MOS, a binsize of $22 = 1.1$ arcsec fits well the camera pixel size, all valid patterns should be included, and the MOS specific bit mask should be used:

         ... ximagebinsize=22 yimagebinsize=22 \
         expression='(PI in [200:500])&&(FLAG==0)&&(PATTERN in [0:12])&&#XMMEA_EM'

in case of the pn, a binsize of $82 = 4.1$ arcsec fits well the camera pixel size, all single and double events should be included, and the PN specific bit mask should be used:

         ... ximagebinsize=82 yimagebinsize=82 \
         expression='(PI in [200:500])&&(FLAG==0)&&(PATTERN in [0:4])&&#XMMEA_EP'

To perform source detection in all the standard pipeline processing energy bands, four more images need to be generated, modifying the energy selection expression in the following way: for image_b2.fits use (PI in [500:2000]), for image_b3.fits use (PI in [2000:4500]), for image_b4.fits use (PI in [4500:7500]) and for image_b5.fits use (PI in [7500:12000]). The energy bands are defined via PI intervals in units of eV. Note that such a multi-band approach to source detection is not essential (source detection can also be performed on a single energy band).

With images extracted in the required energy bands, the user now can start the EPIC source detection process, either performing it step by step (§ 4.12.3.1) or in one go via the edetect_chain meta task (§ 4.12.3.2).