Cosmology with the eROSITA X-ray cluster survey

We analyze the potential and optimization of the upcoming X-ray telescope eROSITA to simultaneously constrain cosmological and X-ray scaling-relation parameters via the measurement of the abundances and angular clustering of galaxy clusters up to z~2. eROSITA will perform an X-ray all-sky survey in about 4 years, after reaching a L2 orbit sometimes in mid 2016: assuming a detection limit of 50 photons in the (0.5-2.0) keV energy band with a typical exposure time of 1.6 ks, we predict that eROSITA will detect about 90’000 clusters more massive than 5x10^13 solar masses.We dedicate special attention to primordial non-Gaussianity (Pillepich et al. 2012) and Dark-Energy models (Pillepich et al. 2015, to be submitted). We discuss our findings by emphasizing the impact onto the cosmological constraints of the uncertainties within the adopted underlying theoretical models and in the mass-observable relations.