The Impact of Cosmic Rays on the Kinematics of the Circumgalactic Medium

Abstract

We use hydrodynamical simulations of two Milky Way-mass galaxies to demonstrate the impact of cosmic-ray pressure on the kinematics of cool and warm circumgalactic gas. Consistent with previous studies, we find that cosmic-ray pressure can dominate over thermal pressure in the inner 50 kpc of the circumgalactic medium (CGM), creating an overall cooler CGM than that of similar galaxy simulations run without cosmic rays. We generate synthetic sightlines of the simulated galaxies' CGM and use Voigt profile fitting methods to extract ion column densities, Doppler-b parameters, and velocity centroids of individual absorbers. We directly compare these synthetic spectral line fits with HST/COS CGM absorption-line data analyses, which tend to show that metallic species with a wide range of ionization potential energies are often kinematically aligned. Compared to the Milky-Way simulation run without cosmic rays, the presence of cosmic-ray pressure in the inner CGM creates narrower OVI absorption features and broader SiIII absorption features, a quality which is more consistent with observational data. Additionally, because the cool gas is buoyant due to nonthermal cosmic-ray pressure support, the velocity centroids of both cool and warm gas tend to align in the simulated Milky Way with feedback from cosmic rays. Our study demonstrates that detailed, direct comparisons between simulations and observations, focused on gas kinematics, have the potential to reveal the dominant physical mechanisms that shape the CGM.

26 pages including 19 figures and appendix. Accepted by ApJ. Updated version includes additional figures, tests, and expanded discussion. Supplemental figures at irynabutsky.me/data

References in corpus (43)

• The Circumgalactic Medium
• Detection of the Characteristic Pion-Decay Signature in Supernova Remnants
• Star Formation and Feedback in Smoothed Particle Hydrodynamic Simulations--I. Isolated Galaxies
• Structural Analysis of Molecular Clouds: Dendrograms
• The COS-Halos Survey: Physical Conditions and Baryonic Mass in the Low-Redshift Circumgalactic Medium
• The COS-Halos Survey: Metallicities in the Low-Redshift Circumgalactic Medium
• A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers
• Characterizing the Circumgalactic Medium of Nearby Galaxies with HST/COS and HST/STIS Absorption-Line Spectroscopy
• Detecting shock waves in cosmological smoothed particle hydrodynamics simulations
• The COS-Dwarfs Survey: The Carbon Reservoir Around sub-L* Galaxies
• The COS-Halos Survey: Origins of the Highly Ionized Circumgalactic Medium of Star-Forming Galaxies
• Cosmic ray feedback in hydrodynamical simulations of galaxy formation
• Multiphase Gas and the Fractal Nature of Radiative Turbulent Mixing Layers
• On the possible environmental effect in distributing heavy elements beyond individual gaseous halos
• The Far Ultraviolet Spectroscopic Explorer Survey of OVI Absorption in the Disk of the Milky Way
• Interaction of a cold cloud with a hot wind: the regimes of cloud growth and destruction and the impact of magnetic fields
• Cosmic ray physics in calculations of cosmological structure formation
• How to quench a galaxy
• Cosmic ray-driven galactic winds: streaming or diffusion?
• 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 Impact of Cosmic Rays on Thermal Instability in the Circumgalactic Medium
• Growth and structure of multiphase gas in the cloud-crushing problem with cooling
• Cosmic-Ray Driven Outflows to Mpc Scales from $L_{\ast }$ Galaxies
• Is Multiphase Gas Cloudy or Misty?
• Effects of Different Cosmic Ray Transport Models on Galaxy Formation
• A signature of anisotropic cosmic-ray transport in the gamma-ray sky
• First Predicted Cosmic Ray Spectra, Primary-to-Secondary Ratios, and Ionization Rates from MHD Galaxy Formation Simulations
• A simple model for mixing and cooling in cloud-wind interactions
• The Survival of Multiphase Dusty Clouds in Hot Winds
• Reconciling cosmic-ray transport theory with phenomenological models motivated by Milky-Way data
• Probing Cosmic Ray Transport with Radio Synchrotron Harps in the Galactic Center
• Detection of hot, metal-enriched outflowing gas around $z\approx$2.3 star-forming galaxies in the Keck Baryonic Structure Survey
• The COS Absorption Survey of Baryon Harbors: Unveiling the Physical Conditions of Circumgalactic Gas through Multiphase Bayesian Ionization Modeling
• Interaction of Cosmic Rays with Cold Clouds in Galactic Halos
• Circumgalactic Pressure Profiles Indicate Precipitation-Limited Atmospheres for $M_{\ast }\sim 10^9$$-$$10^{11.5}{M}_{\odot }$
• Virial shocks are suppressed in cosmic ray-dominated galaxy halos
• A finite volume method for two-moment cosmic-ray hydrodynamics on a moving mesh
• Thermal Instabilities and Shattering in the High-Redshift WHIM: Convergence Criteria and Implications for Low-Metallicity Strong HI Absorbers
• A Consistent Reduced-Speed-of-Light Formulation of Cosmic Ray Transport Valid in Weak and Strong-Scattering Regimes
• One-Two Quench: A Double Minor Merger Scenario
• Role of cosmic rays in the early stages of galactic outflows
• Entropy-Conserving Scheme for Modeling Nonthermal Energies in Fluid Dynamics Simulations

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• Hydrodynamical simulations of the galaxy population: enduring successes and outstanding challenges
• Constraining Cosmic-ray Transport with Observations of the Circumgalactic Medium
• Why are thermally- and cosmic ray-driven galactic winds fundamentally different?
• The Effect of Cosmic Rays on the Observational Properties of the CGM
• IllustrisTNG + Cosmic Rays with a Simple Transport Model: From Dwarfs to L${}^{\star }$ Galaxies
• Strong Evidence for Cosmic Ray-Supported $\sim$L${}^{\ast }$ Galaxy Halos via X-ray \& tSZ Constraints
• Wind of Change: Faraday Rotation in a Simulated Large Magellanic Cloud
• ARCHITECTS I: Impact of subgrid physics on the simulated properties of the circumgalactic medium
• Magnetohydrodynamic turbulence and the associated spatial diffusion tensor of cosmic rays in dynamical galactic halos
• Time-Dependent Cosmic Ray Halos from Bursty Star Formation and Active Galactic Nuclei: Semi-Analytic Formalism and Galaxy Formation Implications