XMM-Newton Science Analysis System


edetect_stack (edetect_stack-0.8.1) [xmmsas_20230412_1735-21.0.0]

Tasks called by edetect_stack

edetect_stack consists of twelve subsequent stages during which ten SAS tasks are called to perform the source detection. While running the meta-task, information on the program flow will be shown if SAS_VERBOSITY or the argument of the option '-V' is set to 5 or higher.

Figure 2 illustrates the flow of standard processing: tasks and products, and indicates how often each task is called.

Figure 2: Structure of edetect_stack.

Notes on the individual task calls.

1. attcalc
   SAS_ODF is set for each attitude file according to the input parameter summarysets and the observation identifier in the files. The analysis area can be chosen by the user via the parameters att_nominalra, att_nominaldec, and att_imagesize which are forwarded to attcalc and activated by with_att_nominalcoord=yes and / or with_att_imagesize=yes.

   When automatically determining the image area, “notOnChip” warnings may be sent by esky2det. They can be ignored. edetect_stack informs the user via an extra warning in case an input pointing does not overlap with the chosen analysis area.

2. evselect
   By default, EPIC images are filtered with the FLAG and pattern expressions that were used for the 2XMM and 3XMM catalogues (described in the 2XMM Catalogue User Guide). Neither explicit gti filtering nor additional pattern filtering of the input event lists are directly supported by edetect_stack. If users want to apply their own filtering expressions, they need to filter the event lists before running edetect_stack and/or create their own input images.

   edetect_stack checks whether output images are empty. Instruments / observations for which no image contains any event are ignored in the following.

3. eexpmap
   Exposure maps are created with withvignetting=no. Vignetted exposure maps are produced in addition, if esp_fitmethod is set to “model (see notes on the call to esplinemap).

4. emask
   The detector masks are created for the lowest energy band per pointing and instruments and applied to all energy bands. Users are advised to check the automatically created detector masks and to adjust the emask thresholds emask_threshold1, emask_threshold1 if, for example, too large regions are masked.

5. eboxdetect (local mode)
   Within edetect_stack, eboxdetect is generally called with exposure maps and detection masks, i.e. the parameters withexpimage and withdetmask are set to “yes” (eboxdetect default: “no”).

6. esplinemap
   edetect_stack supports all fit methods of esplinemap, which are explained in the task description:

   esp_fitmethod=smooth (default of edetect_stack): produce background maps via adaptive smoothing of the cheesed image.

   esp_fitmethod=spline: Use a spline fit to produce the background maps. The number of spline nodes is derived from the image size in pixels, per default, as square root of the longest side divided by two. Users can change the number of nodes by changing the value of the parameter esp_nsplinenodes and setting with_esp_nsplinenodes=true.

   esp_fitmethod=model: pass vignetted exposure maps to esplinemap via the esplinemap parameter expimageset.
   If, additionally, esp_withexpimageset2=true: pass unvignetted exposure maps to esplinemap via the esplinemap parameter expimageset2.

   Users are advised to check the background maps for fit artefacts like very bright regions and to adjust the fit parameters (esp_nsplinenodes or esp_snrmin, esp_smoothsigma) when indicated.

7. eboxdetect (map mode)
   The map-mode box source lists per pointing are used as input to the stacked emldetect run.

8. esensmap
   The creation of sensitivity maps is not mandatory to run the source detection tasks, but recommended for informational purposes. The likelihood threshold mlmin of esensmap, for which the upper limit of source counts is calculated, is set to the minimum detection likelihood of edetect_stack (as given via the parameter mlmin), but not below 1.0.

9. emosaic
   The energy-resolved mosaic images are created for informational purposes only. If five energy bands are used – default in the XMM catalogues –, the images of bands 1 and 2 and of bands 4 and 5 are combined in order to serve as input for RGB images.

10. eboxdetect (stacked, map mode) with emosaic and srcmatch
    1. emosaic is called to create mosaicked images, background maps, exposure maps, and detection masks of all pointings per instrument and energy band.

    2. eboxdetect in map mode is run on the mosaicked images, i.e. on the same number of input images as in standard source detection, to create a preliminary box source list. Its name derived from the parameter eboxs_boxlistset with an inserted “_intermediate”.

       Within edetect_stack, eboxdetect is generally called with exposure maps and detection masks, i.e. the parameters withexpimage and withdetmask are set to “yes” (eboxdetect default: “no”).

    3. srcmatch combines the intermediate stacked box source list with the map-mode box source lists of the individual pointings (if created in stage 7). The output source list is named eboxs_boxlistset.

       The matching radius is determined by edetect_stack from the image binning. If users would like to test different matching radii, they may stop edetect_stack, adjust the value of the parameter maxerr of srcmatch and repeat the matching, before restarting edetect_stack with minstage=11 and the adjusted input list.

    Please note that all the eboxdetect source lists that are produced by edetect_stack serve as input to other tasks and are not suitable for a quantitative analysis.

11. emldetect
    Within edetect_stack, the emldetect source list is an intermediate product, from which the final stacked source list is created. It is produced with withrawrows=yes and, by default, with a lower minimum detection likelihood than the final source list.