Magnetic Fields on FIRE: Comparing B-fields in the multiphase ISM and CGM of Simulated L${}_{\ast }$ Galaxies to Observations

Abstract

The physics of magnetic fields ($\text{B}$) and cosmic rays (CRs) have recently been included in simulations of galaxy formation. However, significant uncertainties remain in how these components affect galaxy evolution. To understand their common observational tracers, we analyze the magnetic fields in a set of high-resolution, magneto-hydrodynamic, cosmological simulations of Milky-Way-like galaxies from the FIRE-2 project. We compare mock observables of magnetic field tracers for simulations with and without CRs to observations of Zeeman splitting and rotation/dispersion measures. We find reasonable agreement between simulations and observations in both the neutral and the ionised interstellar medium (ISM). We find that the simulated galaxies with CRs show weaker ISM $|\text{B}|$ fields on average compared to their magnetic-field-only counterparts. This is a manifestation of the effects of CRs in the diffuse, low density inner circum-galactic medium (CGM). We find that equipartition between magnetic and cosmic ray energy densities may be valid at large ($>$ 1 kpc) scales for typical ISM densities of Milky-Way-like galaxies, but not in their halos. Within the ISM, the magnetic fields in our simulated galaxies follow a power-law scaling with gas density. The scaling extends down to hydrogen number densities $<$ 300 cm${}^{-3}$, in contrast to observationally-derived models, but consistent with the observational measurements. Finally, we generate synthetic rotation measure (RM) profiles for projections of the simulated galaxies and compare to observational constraints in the CGM. While consistent with upper limits, improved data are needed to detect the predicted CGM RMs at 10-200 kpc and better constrain theoretical predictions.

arXiv comment15 pages, 9 figures. Accepted in MNRAS 2022 August 26. Received 2022 August 25; in original form 2022 June 10

References in corpus (69)

• The ATNF Pulsar Catalogue
• Statistical Properties of X-ray Clusters: Analytic and Numerical Comparisons
• Cosmological SPH simulations: A hybrid multi-phase model for star formation
• GIZMO: A New Class of Accurate, Mesh-Free Hydrodynamic Simulation Methods
• FIRE-2 Simulations: Physics versus Numerics in Galaxy Formation
• Gusty, gaseous flows of FIRE: galactic winds in cosmological simulations with explicit stellar feedback
• Diffuse continuum gamma rays from the Galaxy
• A New Model of the Galactic Magnetic Field
• Magnetic Fields in Spiral Galaxies
• Revised equipartition & minimum energy formula for magnetic field strength estimates from radio synchrotron observations
• The Cosmic Baryon Cycle and Galaxy Mass Assembly in the FIRE Simulations
• A Physical Model for the Origin of Quasar Lifetimes
• The CHIME Fast Radio Burst Project: System Overview
• The formation of disc galaxies in high resolution moving-mesh cosmological simulations
• Simulations of magnetic fields in isolated disk galaxies
• The low density and magnetization of a massive galaxy halo exposed by a fast radio burst
• Magnetic fields and spiral arms in the galaxy M51
• Pulsar rotation measures and the magnetic structure of our Galaxy
• The magnetic field and turbulence of the cosmic web measured using a brilliant fast radio burst
• The magnetic field of the Large Magellanic Cloud revealed through Faraday rotation
• Simulations of disk galaxies with cosmic ray driven galactic winds
• But What About... Cosmic Rays, Magnetic Fields, Conduction, & Viscosity in Galaxy Formation
• STARFORGE: Toward a comprehensive numerical model of star cluster formation and feedback
• Radiative transfer with POLARIS: I. Analysis of magnetic fields through synthetic dust continuum polarization measurements
• Accurate, Meshless Methods for Magneto-Hydrodynamics
• Feedback first: the surprisingly weak effects of magnetic fields, viscosity, conduction, and metal diffusion on galaxy formation
• Magnetic fields in cosmological simulations of disk galaxies
• Properties of the Circumgalactic Medium in Cosmic Ray-Dominated Galaxy Halos
• Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV gamma ray emission
• Systematic bias in interstellar magnetic field estimates
• Cooler and smoother -- the impact of cosmic rays on the phase structure of galactic outflows
• Magnetohydrodynamic Simulations of Disk Galaxy Formation: the Magnetization of The Cold and Warm Medium
• The role of cosmic ray pressure in accelerating galactic outflows
• Virialization of the inner CGM in the FIRE simulations and implications for galaxy discs, star formation and feedback
• The Role of Cosmic Ray Transport in Shaping the Simulated Circumgalactic Medium
• Magnetic fields in Local Group dwarf irregulars
• Low-frequency Faraday rotation measures towards pulsars using LOFAR: probing the 3-D Galactic halo magnetic field
• The effects of cosmic rays on the formation of Milky Way-mass galaxies in a cosmological context
• Testing Physical Models for Cosmic Ray Transport Coefficients on Galactic Scales: Self-Confinement and Extrinsic Turbulence at GeV Energies
• The effect of magnetic fields on properties of the circumgalactic medium
• The Impact of Cosmic Rays on Thermal Instability in the Circumgalactic Medium
• Cosmic-Ray Driven Outflows to Mpc Scales from $L_{\ast }$ Galaxies
• The impact of magnetic fields on thermal instability
• New constraints on the magnetization of the cosmic web using LOFAR Faraday rotation observations
• Magnetising the circumgalactic medium of disk galaxies
• Faraday rotation maps of disk galaxies
• Cosmic Rays in Intermittent Magnetic Fields
• A three-phase amplification of the cosmic magnetic field in galaxies
• 3-D gas-phase elemental abundances across the formation histories of Milky Way-mass galaxies in the FIRE simulations: initial conditions for chemical tagging
• Cosmic rays and non-thermal emission in simulated galaxies: III. probing cosmic ray calorimetry with radio spectra and the FIR-radio correlation
• Simulating radio synchrotron emission in star-forming galaxies: small-scale magnetic dynamo and the origin of the far infrared-radio correlation
• DSA-10: A Prototype Array for Localizing Fast Radio Bursts
• Pressure balance in the multiphase ISM of cosmologically simulated disk galaxies
• Evolution of giant molecular clouds across cosmic time
• Ab initio Simulations of a Supernova Driven Galactic Dynamo in an Isolated Disk Galaxy
• A small-scale dynamo in feedback-dominated galaxies - III. Cosmological simulations
• An observational test for correlations between cosmic rays and magnetic fields
• Magnetic fields in the Milky Way from pulsar observations: effect of the correlation between thermal electrons and magnetic fields
• Evolution of galactic magnetic fields
• Constraining Magnetic Fields in the Circumgalactic Medium
• Extragalactic Magnetism with SOFIA (Legacy Program) -- I: The magnetic field in the multi-phase interstellar medium of M51
• Magnetic buoyancy in simulated galactic discs with a realistic circum galactic medium
• The impact of cosmic rays on dynamical balance and disk-halo interaction in Lstar disk galaxies
• On the origin of magnetic driven winds and the structure of the galactic dynamo in isolated galaxies
• Stellar feedback strongly alters the amplification and morphology of galactic magnetic fields
• Virial shocks are suppressed in cosmic ray-dominated galaxy halos
• The Transport of Cosmic Rays Across Magnetic Fieldlines
• A dynamo amplifies the magnetic field of a Milky-Way-like galaxy
• Rotation measure and synchrotron emission signatures in simulations of magnetized galactic discs

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• Standard Self-Confinement and Extrinsic Turbulence Models for Cosmic Ray Transport are Fundamentally Incompatible with Observations
• High resolution modeling of [CII], [CI], [OIII] and CO line emission from the ISM and CGM of a star forming galaxy at z ~ 6.5
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• Time evolution of the galactic $B-\rho$ relation: the impact of the magnetic field morphology
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• Magnetic fields and cosmic rays in M31. II. Strength and distribution of the magnetic field components
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