By N. Cerardi
Our study proposes an exciting new science goal for Athena: the investigation of distant galaxy clusters.
With its unparalleled capability, Athena promises to shed light on both the high-redshift and low-mass segments of the cluster population, as depicted in the inset figure. This is very interesting for cosmology, especially in our understanding of Dark Energy. Our projections suggest that 200 square degrees, 20 ks deep Athena survey could detect over a thousand clusters beyond redshift 1, significantly reducing uncertainty in Dark Energy parameters by a factor of 2.