A trade-off study of the WFI field of view

Abstract

We performed a trade-off study of the Athena WFI field of view (f.o.v.) taking into account a square and a circular f.o.v. In the latter case, the WFI corners would not be exposed to cosmic X-rays and could be used as particle background monitors, simultaneously to the observation. The resulting loss of area would concern only regions of low sensitivity. So, how many and which kind of AGN would be lost? In this poster we report some results derived from simple computations; for both of the two f.o.v. shapes, we folded the Aird+10 XLF with the Athena sky-coverage (assuming the CDF2 configuration and Gamma=1.8) of a deep (700 ks) pointing to derive the number of detectable AGN. Although the absolute numbers are affected by huge uncertainties, the relative numbers (i.e. the fraction of AGN retrieved with the circular f.o.v. with respect to the square f.o.v.) depend only on the different sky-coverages and are therefore much more robust. <P />