eROSITA cluster cosmology forecasts: cluster temperature substructure
  bias
  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. We
want to understand the detection properties and possible bias in temperatures
due to unresolved substructures in the cluster halos. 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. 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. 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.
