Early Science from POSSUM: Shocks, turbulence, and a massive new reservoir of ionised gas in the Fornax cluster

Abstract

We present the first Faraday rotation measure (RM) grid study of an individual low-mass cluster -- the Fornax cluster -- which is presently undergoing a series of mergers. Exploiting commissioning data for the POlarisation Sky Survey of the Universe's Magnetism (POSSUM) covering a $\sim 34$ square degree sky area using the Australian Square Kilometre Array Pathfinder (ASKAP), we achieve an RM grid density of $\sim 25$ RMs per square degree from a 280 MHz band centred at 887 MHz, which is similar to expectations for forthcoming GHz-frequency all-sky surveys. We thereby probe the extended magnetoionic structure of the cluster in unprecedented detail. We find that the scatter in the Faraday RM of confirmed background sources is increased by $16.8\pm 2.4$ rad m${}^{-2}$ within 1 degree (360 kpc) projected distance to the cluster centre, which is 2--4 times more extended than the presently-detectable X-ray-emitting intracluster medium (ICM). The Faraday-active plasma is more massive than the X-ray-emitting ICM, with an average density that broadly matches expectations for the Warm-Hot Intergalactic Medium. The morphology of the Faraday depth enhancement exhibits the classic morphology of an astrophysical bow shock on the southwest side of the main Fornax cluster, and an extended, swept-back wake on the northeastern side. Our favoured explanation is an ongoing merger between the main cluster and a sub-cluster to the southwest. The shock's Mach angle and stand-off distance lead to a self-consistent transonic merger speed with Mach 1.06. The region hosting the Faraday depth enhancement shows a decrement in both total and polarised intensity. We fail to identify a satisfactory explanation for this; further observations are warranted. Generally, our study illustrates the scientific returns that can be expected from all-sky grids of discrete sources generated by forthcoming all-sky radio surveys.

arXiv commentAccepted for publication in PASA. 27 pages, 14 figures, 1 table

References in corpus (110)

• First results from the IllustrisTNG simulations: radio haloes and magnetic fields
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• The GMRT 150 MHz All-sky Radio Survey: First Alternative Data Release TGSS ADR1
• SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. II. The Source Catalogue
• Baryons in the Warm-Hot Intergalactic Medium
• Shocks and cold fronts in galaxy clusters
• Faraday Rotation Measure Synthesis
• The LOFAR Two-metre Sky Survey - I. Survey Description and Preliminary Data Release
• A census of baryons in the Universe from localized fast radio bursts
• GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey I: A low-frequency extragalactic catalogue
• A New Radio - X-Ray Probe of Galaxy Cluster Magnetic Fields
• EMU: Evolutionary Map of the Universe
• SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. I. Science goals, survey design and instrumentation
• eROSITA Science Book: Mapping the Structure of the Energetic Universe
• Particle Acceleration on Megaparsec Scales in a Merging Galaxy Cluster
• A moving cold front in the intergalactic medium of A3667
• GASS: The Parkes Galactic All-Sky Survey. I. Survey Description, Goals, and Initial Data Release
• The Australia Telescope 20 GHz Survey: The Source Catalogue
• GLEAM: The GaLactic and Extragalactic All-sky MWA survey
• Radio and Millimeter Continuum Surveys and their Astrophysical Implications
• The Rapid ASKAP Continuum Survey I: Design and First Results
• The Very Large Array Low-frequency Sky Survey Redux (VLSSr)
• Magnetic Fields and Faraday Rotation in Clusters of Galaxies
• Evolving turbulence and magnetic fields in galaxy clusters
• Substructure and dynamics of the Fornax Cluster
• Science With The Australian Square Kilometre Array Pathfinder
• Draping of Cluster Magnetic Fields over Bullets and Bubbles -- Morphology and Dynamic Effects
• Compact continuum source-finding for next generation radio surveys
• The 2M++ galaxy redshift catalogue
• The Westerbork SINGS Survey II. Polarization, Faraday Rotation, and Magnetic Fields
• Source finding in the era of the SKA (precursors): Aegean 2.0
• Extragalactic Radio Sources and the WMAP Cold Spot
• A radio ridge connecting two galaxy clusters in a filament of the cosmic web
• Not Dead Yet: Cool Circumgalactic Gas in the Halos of Early Type Galaxies
• A2255: the First Detection of Filamentary Polarized Emission in a Radio Halo
• Quasars Probing Quasars VI. Excess HI Absorption Within One Proper Mpc of z~2 Quasars
• Magnetic Field Amplification in Galaxy Clusters and its Simulation
• Magnetic draping of merging cores and radio bubbles in clusters of galaxies
• The intergalactic medium over the last 10 billion years I: Lyman alpha absorption and physical conditions
• Hubble flow around Fornax cluster of galaxies
• On the amplification of magnetic fields in cosmic filaments and galaxy clusters
• Deep ROSAT-HRI observations of the NGC 1399/NGC 1404 region: morphology and structure of the X-ray halo
• Magnetic Fields, Relativistic Particles, and Shock Waves in Cluster Outskirts
• The Physics of Cluster Mergers
• The Origin and Evolution of Cosmic Magnetism
• Structures of the magnetoionic media around the FR I radio galaxies 3C 31 and Hydra A
• Integrated Polarization of Sources at lambda ~1m and New Rotation Measure Ambiguities
• A retrospective view of Miriad
• Hot Atmospheres, Cold Gas, AGN Feedback and the Evolution of Early Type Galaxies: a Topical Perspective
• Faraday Rotation Structure on Kiloparsec Scales in the Giant Radio Lobes of Centaurus A
• Rotation Measures of Radio Sources in Hot Galaxy Clusters
• The Fornax Deep Survey with VST. II. Fornax A: a two-phase assembly caught on act
• Detecting the orientation of magnetic fields in galaxy clusters
• Turbulence and Dynamo in Galaxy Cluster Medium: Implications on the Origin of Cluster Magnetic Fields
• The Australian Square Kilometre Array Pathfinder: Performance of the Boolardy Engineering Test Array
• A Sample of Ultra Steep Spectrum Sources Selected from the Westerbork In the Southern Hemisphere (WISH) survey
• Sardinia Radio Telescope observations of Abell 194 - the intra-cluster magnetic field power spectrum
• Cosmicflows-3: Cosmography of the Local Void
• Suppressed effective viscosity in the bulk intergalactic plasma
• Cold Fronts: Probes of Plasma Astrophysics in Galaxy Clusters
• Differences in Faraday Rotation Between Adjacent Extragalactic Radio Sources as a Probe of Cosmic Magnetic Fields
• The Fornax Deep Survey with VST. V. Exploring the faintest regions of the bright early-type galaxies inside the virial radius
• The Cosmic Large-Scale Structure in X-rays (CLASSIX) Cluster Survey I: Probing galaxy cluster magnetic fields with line of sight rotation measures
• A Combined EIS-NVSS Survey Of Radio Sources (CENSORS) III: Spectroscopic observations
• The challenges of low-frequency radio polarimetry: lessons from the Murchison Widefield Array
• Broadband Radio Polarimetry and Faraday Rotation of 563 Extragalactic Radio Sources
• Thermal plasma in the giant lobes of the radio galaxy Centaurus A
• The Chandra Fornax Survey - I: The Cluster Environment
• Fractional polarization and magnetic fields in the ICM
• Evidence for Merging in the Centaurus Cluster
• Unexpected Circular Radio Objects at High Galactic Latitude
• ATPMN: accurate positions and flux densities at 5 and 8 GHz for 8,385 sources from the PMN survey
• Sample variance, source clustering and their influence on the counts of faint radio sources
• The incidence of cool gas in ~ 1e13 Msun halos
• Ordered magnetic fields around radio galaxies: evidence for interaction with the environment
• On the model of the circumgalactic mist: the implications of cloud sizes in galactic winds and halos
• XMM-Newton Observation of an X-ray Trail Between the Spiral Galaxy NGC6872 and the Central Elliptical NGC6876 in the Pavo Group
• Mg II absorbers: metallicity evolution and cloud morphology
• Degree of Polarization and Source Counts of Faint Radio Sources from Stacking Polarized Intensity
• Structure of the magnetoionic medium around the FR Class I radio galaxy 3C 449
• The distribution of polarized radio sources $>$15$\mu$Jy in GOODS-N
• ATLAS 1.4 GHz Data Release 2 -- II. Properties of the faint polarized sky
• Evolution and Distribution of Magnetic Fields from AGNs in Galaxy Clusters II. The Effects of Cluster Size and Dynamical State
• Gas sloshing regulates and records the evolution of the Fornax Cluster
• The Recent Growth History of the Fornax Cluster Derived from Simultaneous Sloshing and Gas Stripping: Simulating the Infall of NGC 1404
• Dynamics and Magnetization in Galaxy Cluster Cores Traced by X-ray Cold Fronts
• On the reliability of polarization estimation using Rotation Measure Synthesis
• The magnetized medium around the radio galaxy B2 0755+37: an interaction with the intra-group gas
• Warm Gas in the Virgo Cluster: I. Distribution of Lya Absorbers
• A spectroscopic census of the Fornax cluster and beyond: preparing for next generation surveys
• A multiwavelength view of the galaxy cluster Abell 523 and its peculiar diffuse radio source
• Analytic Detection Thresholds for Measurements of Linearly Polarized Intensity Using Rotation Measure Synthesis
• The POlarised GLEAM Survey (POGS) I: First Results from a Low-Frequency Radio Linear Polarisation Survey of the Southern Sky
• The Red Dead Redemption Survey of Circumgalactic Gas About Massive Galaxies. I. Mass and Metallicity of the Cool Phase
• A giant radio bridge connecting two clusters in Abell 1758
• Interacting Large-Scale Magnetic Fields and Ionised Gas in the W50/SS433 System
• The POlarised GLEAM Survey (POGS) II: Results from an All-Sky Rotation Measure Synthesis Survey at Long Wavelengths
• Broadband radio polarimetry of Fornax A, I: Depolarized patches generated by advected thermal material from NGC 1316
• A New Catalog of Faraday Rotation Measures and Redshifts for Extragalactic Radio Sources
• Probing hot gas around luminous red galaxies through the Sunyaev-Zel'dovich effect
• The Redshift Distribution of FIRST Radio Sources at 1 mJy
• Characterizing the Uncertainty in Cluster Magnetic Fields derived from Rotation Measures
• Preliminary evidence for a virial shock around the Coma galaxy cluster
• The Combined NVSS-FIRST Galaxies (CoNFIG) Sample - I. Sample Definition, Classification and Evolution
• Radio galaxies and their magnetic fields out to z <= 3
• A Broadband Spectro-polarimetric View of the NVSS Rotation Measure Catalogue II: Effects of Off-axis Instrumental Polarisation
• Deconstructing the Antlia cluster core
• Detection of Metal-Rich, Cool-Warm Gas in the Outskirts of Galaxy Clusters
• Optimum Frequency of Faraday Tomography to Explore the Inter-Galactic Magnetic Field in Filaments of Galaxies
• The Fornax Deep Survey (FDS) with the VST: III. Low Surface Brightness (LSB) dwarfs and Ultra Diffuse Galaxies (UDGs) in the center of the Fornax cluster

Cited by in corpus (21)

• The Second Radio Synchrotron Background Workshop: Conference Summary and Report
• A Radio Polarisation Study of Magnetic Fields in the Small Magellanic Cloud
• The Spiderweb proto-cluster is being magnetized by its central radio jet
• Characterising the turbulent multiphase halos with periodic box simulations
• The spectrum of magnetized turbulence in the interstellar medium
• The MeerKAT Fornax Survey IV. A close look at the cluster physics through the densest rotation measure grid
• Intergalactic medium rotation measure of primordial magnetic fields
• Message in a Bottle: Unveiling the Magneto-Ionic Complexity of AGNs through the Stokes QU-Fitting Technique
• A depolarizing HI tidal tail in the western lobe of Fornax A
• The SRG/eROSITA all-sky survey: View of the Fornax galaxy cluster
• A 600 kpc complex radio source at the center of Abell 3718 discovered by the EMU and POSSUM surveys
• The Galactic latitude dependency of Faraday complexity in the S-PASS/ATCA RM catalogue
• Distant probes of RM structure -- Where is the Faraday Rotation towards the Magellanic Leading Arm?
• The technological and scientific development of ASKAP
• Supersonic turbulence simulations with GPU-based high-order Discontinuous Galerkin hydrodynamics
• OLIMPO: a Balloon-Borne SZE Imager to Probe ICM Dynamics and the WHIM
• Relighting the fire in Hickson Compact Group (HCG) 15: magnetised fossil plasma revealed by the SKA Pathfinders & Precursors
• Magnetic Fields in the Shapley Supercluster Core with POSSUM: Challenging Model Predictions
• Wind of Change: Faraday Rotation in a Simulated Large Magellanic Cloud
• Interaction Between Rogue HI Clouds and the Magnetic Field High Above the Galaxy
• Testing the correlation between bending angle and polarization properties of bent radio galaxies