Full-sky photon simulation of clusters and active galactic nuclei in the
  soft X-rays for eROSITA
  The eROSITA X-ray telescope on board the Spectrum-Roentgen-Gamma (SRG)
mission will measure the position and properties of about 100,000 clusters of
galaxies and 3 million active galactic nuclei over the full sky. To study the
statistical properties of this ongoing survey, it is key to estimate the
selection function accurately. We create a set of full sky light-cones using
the MultiDark and UNIT dark matter only N-body simulations. We present a novel
method to predict the X-ray emission of galaxy clusters. Given a set of dark
matter halo properties (mass, redshift, ellipticity, offset parameter), we
construct an X-ray emissivity profile and image for each halo in the
light-cone. We follow the eROSITA scanning strategy to produce a list of X-ray
photons on the full sky. We predict scaling relations for the model clusters,
which are in good agreement with the literature. The predicted number density
of clusters as a function of flux also agrees with previous measurements.
Finally, we obtain a scatter of 0.21 (0.07, 0.25) for the X-ray luminosity --
mass (temperature -- mass, luminosity -- temperature) model scaling relations.
We provide catalogues with the model photons emitted by clusters and active
galactic nuclei. These catalogues will aid the eROSITA end to end simulation
flow analysis and in particular the source detection process and cataloguing
methods.
