Full-sky photon simulation of clusters and active galactic nuclei in the soft X-rays for eROSITA

TL;DR

This paper develops a comprehensive simulation of full-sky X-ray emissions from galaxy clusters and active galactic nuclei to support the eROSITA survey, including novel methods for predicting cluster X-ray emission and creating realistic photon catalogs.

Contribution

It introduces a new method to predict X-ray emission from galaxy clusters based on dark matter halo properties and generates full-sky photon catalogs for eROSITA, aiding survey analysis.

Findings

Predicted cluster number density matches previous measurements.

Scaling relations for clusters are consistent with literature.

Catalogs of model photons support survey analysis.

Abstract

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.