Quantify Chandra/XMM single-temperature bias from multiphase gas and its impact on eROSITA cross-calibration

Ascertain the extent to which single-temperature spectral fits to multi-temperature intracluster medium bias the temperatures measured with Chandra/ACIS and XMM-Newton/EPIC, and derive the consequent effect on the temperature cross-calibration between SRG/eROSITA and these instruments.

Background

The paper uses hydrodynamical simulations to show that single-temperature fits to eROSITA data underestimate the mass-weighted or emission-weighted temperatures of galaxy clusters by tens of percent, implying possible biases that could contribute to cross-calibration discrepancies with Chandra and XMM-Newton. However, analogous simulation-based assessments for Chandra/ACIS and XMM-Newton/EPIC have not yet been performed.

Because Chandra and XMM-Newton likely also suffer single-temperature fitting biases when the intracluster medium is multiphase, the authors note that without a comparable analysis for these instruments, the net impact on the eROSITA-versus-Chandra/XMM temperature comparison cannot be determined. Establishing this will clarify the role of multiphase gas in cross-calibration differences.

References

Until a similar analysis is performed for these two X-ray instruments, it is unclear exactly how the T comparison between them and eROSITA would be affected.

— The SRG/eROSITA All-Sky Survey: SRG/eROSITA cross-calibration with Chandra and XMM-Newton using galaxy cluster gas temperatures  (2401.17297 - Migkas et al., 2024) in Section 5.2.1 (Multi-temperature gas structure – Simulations from past studies)