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arXiv · 2610.16741

The XMM Cluster Survey: Cross-Calibration of eROSITA and XMM using Dark Energy Survey Y3 Galaxy Clusters

J. E. Pilling·D. J. Turner·P. A. Giles·A. K. Romer·R. Wilkinson·P. J. Rooney·M. Hilton·S. Bhargava·J. Hall·R. Wang·A. Abdulghafour·B. J. Maughan
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Abstract

We present the cross-calibration of the eROSITA and XMM telescopes, using galaxy clusters detected by redMaPPer from the first three years of Dark Energy Survey observations (DESY3RM). We use the X-ray: Generate and Analyse (XGA) Python module to measure eROSITA properties, and validate our methodology using a deep pointed eROSITA CAL-PV observation of A3158, and a sample of 119 clusters from the expanded HIgh FLux Galaxy Cluster Sample (eeHiFLUGCS). Next, we construct a sample of DESY3RM clusters matched to XMM observations analysed by the XMM Cluster Survey (XCS), and to clusters in the first release of the eROSITA All-Sky Survey (eRASS1). This produced a sample of 114 DESY3RM clusters with both XMM and eROSITA detections. Our resulting X-ray temperatures determined from eROSITA were compared to eRASS1 catalogue values, showing consistency between the two analyses. Comparisons between XMM and eROSITA temperatures reveal a systematic offset, with XMM temperatures 28$\pm$7% higher on average. Finally, we fit $L_{\rm X,soft}$-$λ_{\rm RM}$ and $T_{\rm X}$-$λ_{\rm RM}$ scaling relations for both eROSITA and XMM using the same cluster sample, finding minimal differences in the $L_{\rm X,soft}$-$λ_{\rm RM}$ relation but a clear normalisation offset in the $T_{\rm X}$-$λ_{\rm RM}$ relation, particularly for the highest richness systems. This study will enable future work combining eROSITA and XMM observatories for DESY3RM clusters.

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J. E. Pilling, D. J. Turner, P. A. Giles, A. K. Romer, R. Wilkinson, P. J. Rooney, M. Hilton, S. Bhargava, J. Hall, R. Wang, A. Abdulghafour, B. J. Maughan. 2026-10-12. The XMM Cluster Survey: Cross-Calibration of eROSITA and XMM using Dark Energy Survey Y3 Galaxy Clusters. https://arxiv.org/abs/2610.16741

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