Testing X‐Ray Measurements of Galaxy Clusters with Cosmological Simulations

X-ray observations of galaxy clusters potentially provide powerfulcosmological probes if systematics due to our incomplete knowledge of theintracluster medium (ICM) physics are understood and controlled. In this paper,we present mock Chandra analyses of cosmological cluster simulations and assessX-ray measurements of galaxy cluster properties using a model and procedureessentially identical to that used in real data analysis. We show thatreconstruction of three-dimensional ICM density and temperature profiles isexcellent for relaxed clusters, but still reasonably accurate for unrelaxedsystems. The total ICM mass is measured quite accurately (<6%) in all clusters,while the hydrostatic estimate of the gravitationally bound mass is biased lowby about 5%-20% through the virial region, primarily due to additional pressuresupport provided by subsonic bulk motions in the ICM, ubiquitous in oursimulations even in relaxed systems. Gas fraction determinations are thereforebiased high; the bias increases toward cluster outskirts and dependssensitively on its dynamical state, but we do not observe significant trends ofthe bias with cluster mass or redshift. We also find that different average ICMtemperatures, such as the X-ray spectroscopic Tspec and gas-mass-weighted Tmg,are related to each other by a constant factor with a relatively smallobject-to-object scatter and no systematic trend with mass, redshift or thedynamical state of clusters. We briefly discuss direct applications of ourresults for different cluster-based cosmological tests.Comment: 11 pages, 6 figures, submitted to Ap