Average energy of the X-ray spectrum as a model-independent proxy for the mass of galaxy clusters

Abstract

Temperature of the hot gas in galaxy clusters is known to be a reliable proxy for their total gravitating mass, allowing one to use spectroscopic X-ray observations for halo mass function measurements. Data of shallow wide area surveys, however, often precludes direct fitting of the X-ray spectra, given possible biases arising due to unresolved (multi-temperature) inner structure of the intracluster medium (ICM), projection effects and necessity of certain model assumptions to be made to allow for robust spectral fitting. We consider using a simple observable value - the average energy of the observed cluster X-ray spectrum - as a model-independent proxy for the ICM temperature, and consequently cluster's mass. We calibrate relation of this proxy to the cluster parameters using mock observations for a sample of 84 massive galaxy clusters extracted from the \textit{Magneticum} cosmological hydro simulations. We consider observational parameters corresponding to the all-sky survey observations by \textit{SRG/eROSITA}. Taking into account contributions of various background and foreground signals, average energy of the simulated X-ray spectra in the $0.4-7.0$ keV band is shown to be a stable indicator of the ICM temperature with $\sim 10\%$ scatter and cluster's mass $M_{500}$ with a $\sim 20\%$ scatter. A database containing simulated X-ray images and their spectra (subtracted in several concentric rings) is publicly available.

23 pages, 12 figures, accepted by JCAP

References in corpus (18)

• The SRG X-ray orbital observatory, its telescopes and first scientific results
• The SRG/eROSITA all-sky survey: First X-ray catalogues and data release of the western Galactic hemisphere
• XMM-Newton and Chandra Cross Calibration Using HIFLUGCS Galaxy Clusters: Systematic Temperature Differences and Cosmological Impact
• Abundance and temperature of the outer hot circum-Galactic medium: The SRG/eROSITA view of the soft X-ray background in the eFEDS field
• Offset between X-ray and optical centers in clusters of galaxies: connecting eROSITA data and simulations
• The Cosmological Simulation Code OpenGadget3 -- Implementation of Meshless Finite Mass
• The eROSITA view of the Abell 3391/95 field: a case study from the Magneticum cosmological simulation
• Mapping "out-of-the-box" the properties of the baryons in massive halos
• (No) dimming of X-ray clusters beyond z~1 at fixed mass: crude redhshifts and masses from raw X-ray and SZ data
• Can Chandra resolve the remaining cosmic X-ray background?
• A multi-simulation study of relativistic SZ temperature scalings in galaxy clusters and groups
• The SRG/eROSITA All-Sky Survey: SRG/eROSITA cross-calibration with Chandra and XMM-Newton using galaxy cluster gas temperatures
• Decomposition of galactic X-ray emission with Phox: Contributions from hot gas and XRBs
• Detecting Galaxy Groups and AGNs populating the local Universe in the eROSITA era
• X-ray surface brightness and gas density profiles of galaxy clusters up to 3*R500c with SRG/eROSITA
• Effects of Multiphase Gas and Projection on X-ray Observables in Simulated Galaxy Clusters as Seen by eROSITA
• Hydrostatic Mass Profiles of Galaxy Clusters in the eROSITA Survey
• Low-scatter galaxy cluster mass proxies for the eROSITA all-sky survey

Cited by in corpus (1)

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