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arfgen (arfgen-1.102) [xmmsas_20211130_0941-20.0.0]


Different types of detector map

A detector map is used to provide a grid of positions over which to calculate and flux weight the ARF. The default detector map is 'flat' which has a weighting of 1.0 for each detector map pixel and is rectangular having sides which just encompass the region specified in the DSS. Only detector map pixels falling within the source region are included in the ARF calculation, e.g. for a circular source box, the pixels in the corners of the detector map will be ignored. The number of detector map pixels is set automatically unless explicitely set with the parameters detxbins and detybins. The calculated number of pixels in each dimension is constrained to be between 5 and 80, and is set proportionately to the total extent of the extraction region. The total extent is taken from the included and excluded regions and for example can be surprisingly large if detected sources have been removed by excluding regions.

Some fine regions, e.g. a narrow annulus at a large off-axis angle, may not be well represented by the default map. In these cases more map pixels can be introduced by specifying e.g. detxbins=100, detybins=100, but beware that the task execution time increases with the number of bins.

arfgen supports 3 types of detector map, selectable through the detmaptype parameter:

XMM-Newton SOC -- 2021-11-30