The effect of magnetic fields on properties of the circumgalactic medium

Voort, Freeke van de; Bieri, Rebekka; Pakmor, Rüdiger; Gómez, Facundo A.; Grand, Robert J. J.; Marinacci, Federico

doi:10.1093/mnras/staa3938

Cited by 84 publications

(28 citation statements)

References 85 publications

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“…Magnetic fields are an important component of the ISM of starforming galaxies. They provide additional support against gravity (Boulares & Cox 1990), heat up the gas via magnetic reconnection (Raymond 1992), alter the gas flow (Shetty & Ostriker 2006), reduce the efficiency of star formation (Federrath 2015), control the propagation of cosmic rays (Cesarsky 1980;Shukurov et al 2017), affect galactic outflows (van de Voort et al 2021), and might also play a role in the galaxy's evolution (Pakmor & Springel 2013). Thus, it is important to study the strength, structure, and evolution of magnetic fields in galaxies.…”

Section: Introductionmentioning

confidence: 99%

Turbulent dynamo in the two-phase interstellar medium

Seta,

Federrath

2022

Preprint

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Magnetic fields are a dynamically important component of the turbulent interstellar medium (ISM) of star-forming galaxies. These magnetic fields are due to a dynamo action, which is a process of converting turbulent kinetic energy to magnetic energy. A dynamo that acts at scales less than the turbulent driving scale is known as the turbulent dynamo. The ISM is a multiphase medium and observations suggests that the properties of magnetic fields differ with the phase. Here, we aim to study how the properties of the turbulent dynamo depend on the phase. We simulate the non-isothermal turbulent dynamo in a two-phase medium (most previous work assumes an isothermal gas). We find that the growth rate of magnetic fields in the exponentially growing stage is similar in both the phases, and this is because of a roughly equal amount of vorticity being generated in each phase. We further compute each term responsible for amplification and destruction of vorticity and show that the amplification of vorticity by turbulent motions is a dominant term (similar in both the phases) followed by the baroclinic term (only present in non-isothermal gases, higher in the warm phase) and the term for viscous interactions in the presence of logarithmic density gradients (higher in the cold phase). We find that the final ratio of magnetic to turbulent kinetic energy is lower due to a stronger Lorentz force. We find that the non-isothermal turbulent dynamo is less efficient than its isothermal counterpart.

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Section: Introductionmentioning

confidence: 99%

Turbulent dynamo in the two-phase interstellar medium

Seta,

Federrath

2022

Preprint

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“…In recent years, the impact of non-thermal processes on the halo gas, such as magnetic fields (e.g. Ji, Oh & McCourt 2018;van de Voort et al 2020) and cosmic rays (CRs; e.g. Salem, Bryan & Corlies 2016;Farber et al 2018;Ji et al 2020;Buck et al 2020;Butsky et al 2020), is under increasingly active investigation.…”

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confidence: 99%

Virial shocks are suppressed in cosmic ray-dominated galaxy haloes

Kereš

Chan

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We study the impact of cosmic rays (CRs) on the structure of virial shocks, using a large suite of high-resolution cosmological FIRE-2 simulations accounting for CR injection by supernovae. In Milky Way-mass, low-redshift (z ≲ 1−2) haloes, which are expected to form ‘hot haloes’ with slowly cooling gas in quasi-hydrostatic equilibrium (with a stable virial shock), our simulations without CRs do exhibit clear virial shocks. The cooler phase condensing out from inflows becomes pressure confined to overdense clumps, embedded in low-density, volume-filling hot gas with volume-weighted cooling time longer than inflow time. The gas thus transitions sharply from cool free-falling inflow, to hot and thermal-pressure supported at approximately the virial radius (≈Rvir), and the shock is quasi-spherical. With CRs, we previously argued that haloes in this particular mass and redshift range build up CR-pressure-dominated gaseous haloes. Here, we show that when CR pressure dominates over thermal pressure, there is no significant virial shock. Instead, inflowing gas is gradually decelerated by the CR pressure gradient and the gas is relatively subsonic out to and even beyond Rvir. Rapid cooling also maintains subvirial temperatures in the inflowing gas within ∼Rvir.

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“…Thus, for the unmagnetized case, we expect instability happens in the Milky Way in the SM mDM case for [q χ /m χ ] > 10 −4 and for the dark U (1) charge for [q χ /m χ ] > 10 −13 . The constraints on the former case are even much stronger when we include magnetic fields, as discussed in § 4.4, and Milky Way-like dark matter halos may harbor ∼ 1µG magnetic fields [38].…”

Section: The Milky Way Systemmentioning

confidence: 93%

Astrophysical Plasma Instabilities induced by Long-Range Interacting Dark Matter

Cruz¹,

McQuinn²

2022

Preprint

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If dark matter is millicharged or darkly charged, collective plasma processes may dominate momentum exchange over direct particle collisions. In particular, plasma streaming instabilities can couple the momentum of the dark matter to counter-streaming baryons or other dark matter and result in the counter-streaming fluids coming to rest with each other, just as happens for baryonic collisionless shocks in astrophysical systems. While electrostatic plasma instabilites (such as the two stream) are highly suppressed by Landau damping in the cosmological situations of interest, electromagnetic instabilities such as the Weibel can couple the momenta. Their growth rates are slower than the prior assumption that they would grow at the plasma frequency of the dark matter. We find that the streaming of dark matter in the pre-Recombination universe is affected more strongly by direct collisions than collective processes, validating previous constraints. However, when considering unmagnetized instabilities the properties of the Bullet Cluster merger and other merging cluster systems (which show dark matter streaming through itself) would be substantially altered if [q χ /m χ ] 10 −4 , where [q χ /m χ ] is the charge-to-mass ratio of the dark matter relative to that of the proton. When a magnetic field is added consistent with cluster observations, both the Weibel and Firehose instabilities result in the constraint [q χ /m χ ] 10 −12 − 10 −11 . The constraints are even stronger in the case of a dark U (1) charge (because "hot" electrons do not damp the instability), ruling out [q χ /m χ ] 10 −14 in the Bullet Cluster system. The strongest previous limits on millicharged dark matter (mDM) arise from considering the spin down of galactic disks [1]. We show that plasma instabilities or tangled background magnetic fields could lead to diffusive propagation of the dark matter, weakening these spin down limits. Thus, our constraints from considering plasma instabilities are the most stringent over much of the millicharged and especially dark-charged parameter space.

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The effect of magnetic fields on properties of the circumgalactic medium

Cited by 84 publications

References 85 publications

Turbulent dynamo in the two-phase interstellar medium

Turbulent dynamo in the two-phase interstellar medium

Virial shocks are suppressed in cosmic ray-dominated galaxy haloes

Astrophysical Plasma Instabilities induced by Long-Range Interacting Dark Matter

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