### Abstract

Contributed Talk - Splinter eROSITA

Thursday, 21 September 2017, 14:35   (HS4)

## The X-ray cluster survey with eROSITA: constraints on dark-energy

A. Pillepich1, T. Reiprich2, C. Porciani2
1Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
2Argelander-Institut für Astronomie, Auf dem Hügel 71, D-53121 Bonn, Germany

We forecast the potential of the X-ray galaxy-cluster telescope eROSITA to constrain Dark-Energy models. We focus on spatially-flat cosmological scenarios with either constant or time-dependent Dark-Energy equation of state parameters. The results are given by the combination of the abundance and spatial clustering of a synthetic photon-count limited sample of clusters of galaxies up to z\sim2. We quantify our findings according to different scenarios for the availability of 1) X-ray follow-up observations, 2) photometric and spectroscopic redshifts, and 3) accurate knowledge of the observable - mass relation down to the scale of groups of galaxies. With 10^5 clusters from an average all-sky exposure of 1.6 ks (with at least 50 photons each), eROSITA will give marginalized, one-dimensional, 1\sigma errors of \Delta \sigma_8 = 0.008 (\sim1%), \Delta \Omega_m = 0.006 (2.2%), \Delta w_0 = 0.07 (7%), and \Delta w_a = 0.27 (optimistic scenario), in combination with and largely improving upon Planck data from the temperature anisotropies of the Cosmic Microwave Background.