Galaxy clusters trace the highest peaks in the cosmic density field and offer an independent and powerful probe of the growth of structure, because their abundance and its evolution is strongly dependent on the underlying cosmology. The availability of the new all sky survey of groups and galaxy clusters in the X-ray band with eROSITA will put us on the verge of a breakthrough astrophysics and in precision cosmological measurements. I will present the first results on clusters of galaxies from the eROSITA Final Equatorial Survey performed during the Performance Verification phase and describe the X-ray properties of of the massive clusters detected in the first All-sky Survey.
First Results from eROSITA Observations of Galaxy Groups and Clusters