Magnetic Fields in the Shapley Supercluster Core with POSSUM: Challenging Model Predictions

Abstract

Faraday Rotation Measure (RM) Grids provide a sensitive means to trace magnetized plasma across a wide range of cosmic environments. We study the RM signal from the Shapley Supercluster Core (SSC), in order to constrain the magnetic field properties of the gas. The SSC region consists of two galaxy clusters A3558 and A3562, and two galaxy groups between them, at $z\simeq 0.048$. We combine RM Grid data with thermal Sunyaev-Zeldovich effect data, obtained from the POSSUM pilot survey, and Planck, respectively. To robustly determine the gas density, its magnetic field properties, and their correlation, we study the RM scatter in the SSC region and its behavior as a function of distance to the nearest cluster/group. We compare observational results with semi-analytic Gaussian random field models and more realistic cosmological MHD simulations. With a sky-density of 36 RMs/deg${}^2$, we detect an excess RM scatter of $30.5\pm 4.6rad/{\mathrm{m}}^2$ in the SSC region. Comparing with models, we find an average magnetic field strength of 1-3 $\mu$G (in the groups and clusters). The RM scatter profile, derived from data ranging from 0.3-1.8 $r_{500}$ for all objects, is systematically flatter than expected compared to models, with $\eta <0.5$ being favored. Despite this discrepancy, we find that cosmological MHD simulations matched to the SSC structure most closely align with scenarios where the magnetic field is amplified by the turbulent velocity in the intercluster regions on scales $\lesssim 0.8r_{500}$. The dense RM grid and precision provided by POSSUM allows us to probe magnetized gas in the SSC clusters and groups on scales within and beyond their $r_{500}$. Flatter-than-expected RM scatter profiles reveal a significant challenge in reconciling observations with even the most realistic predictions from cosmological MHD simulations in the outskirts of interacting clusters.

23 pages, 15 figures. Accepted for publication in A&A

References in corpus (60)

• The Simons Observatory: Science goals and forecasts
• Cosmicflows-2: The Data
• A census of baryons in the Universe from localized fast radio bursts
• The Baryon Census in a Multiphase Intergalactic Medium: 30% of the Baryons May Still Be Missing
• Magnetic Field in Clusters of Galaxies
• The Coma cluster magnetic field from Faraday rotation measures
• Observations of the MIssing Baryons in the warm-hot intergalactic medium
• Magnetic Fields and Faraday Rotation in Clusters of Galaxies
• Astrophysics with the Spatially and Spectrally Resolved Sunyaev-Zeldovich Effects: A Millimetre/Submillimetre Probe of the Warm and Hot Universe
• Planck 2018 results. XI. Polarized dust foregrounds
• An MHD Gadget for cosmological simulations
• Radio polarization from the inner Galaxy at arcminute resolution
• MILCA, a Modified Internal Linear Combination Algorithm to extract astrophysical emissions from multi-frequency sky maps
• Probing the missing baryons with the Sunyaev-Zel'dovich effect from filaments
• The intracluster magnetic field power spectrum in Abell 2255
• Magnetic Field Amplification in Galaxy Clusters and its Simulation
• Outskirts of Galaxy Clusters
• A non-ideal MHD Gadget: Simulating massive galaxy clusters
• The intracluster magnetic field power spectrum in Abell 2382
• Rotation Measures of Radio Sources in Hot Galaxy Clusters
• Measurements and simulation of Faraday rotation across the Coma radio relic
• Temperature structure of the intergalactic medium within seven nearby and bright clusters of galaxies observed with XMM-Newton
• Sardinia Radio Telescope observations of Abell 194 - the intra-cluster magnetic field power spectrum
• The intracluster magnetic field power spectrum in A2199
• Missing Baryons and the Warm-Hot Intergalactic Medium
• Source-finding for the Australian Square Kilometre Array Pathfinder
• Dynamical evolution of magnetic fields in the intracluster medium
• The Cosmic Large-Scale Structure in X-rays (CLASSIX) Cluster Survey I: Probing galaxy cluster magnetic fields with line of sight rotation measures
• Magnetic Fields and Ionized Gas in the inner Galaxy: An Outer Scale for Turbulence and the Possible Role of HII Regions
• Faraday Rotation Measure due to the Intergalactic Magnetic Field II: the Cosmological Contribution
• Constrained hyperbolic divergence cleaning in smoothed particle magnetohydrodynamics with variable cleaning speeds
• The correct sense of Faraday rotation
• Radio footprints of a minor merger in the Shapley Supercluster: From supercluster down to galactic scales
• Magnetic field evolution in cosmic filaments with LOFAR data
• The intra-cluster magnetic field in the double relic galaxy cluster Abell 2345
• Detection of intercluster gas in superclusters using the thermal Sunyaev-Zel'dovich effect
• Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster
• The Cosmological Simulation Code OpenGadget3 -- Implementation of Meshless Finite Mass
• Simulating the LOcal Web (SLOW): I. Anomalies in the local density field
• The detection of cluster magnetic fields via radio source depolarisation
• Adaptive mesh refinement simulations of a galaxy cluster merger - I. Resolving and modelling the turbulent flow in the cluster outskirts
• RMTable2023 and PolSpectra2023: standards for reporting polarization and Faraday rotation measurements of radio sources
• On the small scale turbulent dynamo in the intracluster medium: A comparison to dynamo theory
• Galaxy clusters in local Universe simulations without density constraints: a long uphill struggle
• Exploring the relation between turbulent velocity and density fluctuations in the stratified intracluster medium
• Linking a universal gas density profile to the core-excised X-ray luminosity in galaxy clusters up to z ~ 1.1
• Characterizing the Uncertainty in Cluster Magnetic Fields derived from Rotation Measures
• The challenge of measuring and mapping the missing baryons
• Probing cluster magnetism with embedded and background radio sources in Planck clusters
• The thermal and non-thermal components within and between galaxy clusters Abell 399 and Abell 401
• The MeerKAT Fornax Survey IV. A close look at the cluster physics through the densest rotation measure grid
• Simulating the LOcal Web (SLOW) II: Properties of local galaxy clusters
• On the nature of LOFAR RMs and new constraints on magnetic fields in cosmic filaments and on magnetogenesis scenarios
• Shapley Supercluster Survey: mapping the dark matter distribution
• Magnetic fields in the outskirts of PSZ2 G096.88+24.18 from depolarization analysis of radio relics
• Simulating the LOcal Web (SLOW) -- III: Synchrotron emission from the local cosmic web
• Faraday tomography of LoTSS-DR2 data: II. Multi-tracer analysis in the high-latitude outer Galaxy
• Faraday Rotation Measure Dependence on Galaxy Clusters Dynamics
• Vortex-p: a Helmholtz-Hodge and Reynolds decomposition algorithm for particle-based simulations
• Constraining the magnetic field in the galaxy cluster Abell 2142 using MeerKAT L-band polarisation data