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Analysis of extended sources is complex, challenging and time-consuming. There is currently neither an official SAS recipe, nor a simple thread. The XMM-Newton EPIC Background Working Group (BGWG) was therefore founded in 2005 as a steering and supervising committee to provide the users with clear information on the EPIC Background and (SAS)-tools to treat the background correctly for various scenarios. Although the group stopped its main activities in 2012 the SOC is still responsible for maintaining some of its products.
The progress of the XMM-Newton EPIC Background working group is available at:
http://www.cosmos.esa.int/web/xmm-newton/background
which contains information and tools collected and documented by the
Background Working Group during its 7 years of existence. A summary of
the contents of these pages is collected below:
Since SAS v16, it is possible to access the FWC repository through the SAS task evqpb to produce a tailored FWC event file suitable for a given science exposure. evqpb only deals with EPIC-pn and EPIC-MOS Full Frame mode exposures. Also, as of SAS v19, a new task has been introduced, qpbselect, to deal with the QPB in science exposures. qpbselect expands the functionality of evqpb by using the number of discarded lines (NDISCLIN) to estimate the level of the QPB affecting a given science EPIC exposure. The task will produce a corresponding QPB event file, image and spectrum that can be used to correct the science data. This method is only valid for EPIC-pn, and as of SASv21, applicable only to Full Frame and Extended Full Frame mode data. It is recommended not to use these files for other modes since the instrumental noise depends on the exposure mode used. A dedicated thread explains how to produce and deal with tailored FWC event files to account for the QPB in a given science exposure,
https://www.cosmos.esa.int/web/xmm-newton/sas-thread-background
One of the main problems in the analysis of extended sources is that often no statistically useful blank background region can be defined in the observational field-of-view. A workaround is to make use of the provided 'blank sky' background files to generate background spectra corresponding to the camera/mode/filter combination rescaled to the actual observation.
An alternative approach is to model the background spectra based on the background conditions of the individual observation under study. The recommended method is to make use of the Extended Source Analysis Software (XMM-ESAS) package. As of SAS v9.0, this package is integrated in SAS. The list of XMM-ESAS packages integrated in SAS can be found here:
http://xmm-tools.cosmos.esa.int/external/sas/current/doc/esas/
The XMM-ESAS package allows to model the quiescent particle background both spectrally and spatially for the pn and MOS detectors. XMM-ESAS produces background spectra for user-defined regions of the detectors and background images. As of SAS v21, ESAS has suffered a significant improvement where the ESAS routines have been made less dependent upon the rigid directoryfile name structure of past versions, and have been made more modular. There is an XMM-ESAS Cookbook [39] and three SAS Analysis Threads that describe how to use XMM-ESAS step-by-step.
A description of how to use an image from another instrument to correct for flux lost in an extended image, due to chip gaps and bad pixels, is given in the arfgen user guide and in the Technical Note CAL-TN-0227.
Suggestions and caveats on the analysis of extended sources with the EPIC cameras have also been addressed in a SAS workshop presentation (available from the SAS Workshop page).
European Space Agency - XMM-Newton Science Operations Centre