eROSITA cluster cosmology forecasts: Cluster temperature substructure bias
1 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany
2 CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
3 Université de Toulouse, UPS-OMP, IRAP, 31013 Toulouse, France
4 Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
5 Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland
Received: 7 March 2017
Accepted: 16 August 2017
Context. The eROSITA mission will provide the largest sample of galaxy clusters detected in X-ray to date (one hundred thousand expected). This sample will be used to constrain cosmological models by measuring cluster masses. An important mass proxy is the electron temperature of the hot plasma detected in X-rays.
Aims. We want to understand the detection properties and possible bias in temperatures due to unresolved substructures in the cluster halos.
Methods. We simulated a large number of galaxy cluster spectra with known temperature substructures and compared the results from analysing eROSITA simulated observations to earlier results from Chandra.
Results. We were able to constrain a bias in cluster temperatures and its impact on cluster masses, as well as cosmological parameters derived from the survey. We found temperatures in the eROSITA survey to be biased low by about five per cent due to unresolved temperature substructures (compared to emission-weighted average temperatures from the Chandra maps). This bias would have a significant impact on the eROSITA cosmology constraints if not accounted for in the calibration.
Conclusions. We isolated the bias effect that substructures in galaxy clusters have on temperature measurements and their impact on derived cosmological parameters in the eROSITA cluster survey.
Key words: galaxies: clusters: general / X-rays: galaxies: clusters / cosmological parameters
© ESO, 2017