The Launching of Cold Clouds by Galaxy Outflows. III. The Influence of Magnetic Fields

Cottle, J’Neil; Scannapieco, Evan; Brüggen, M.; Banda-Barragán, Wladimir; Federrath, Christoph

doi:10.3847/1538-4357/ab76d1

Cited by 43 publications

(25 citation statements)

References 68 publications

(97 reference statements)

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“…The smaller amount of cool clouds dispersed throughout the MHD halo may be a consequence of evaporation as the surrounding medium is hotter in this run as compared to the Hydro case. Furthermore, it has been shown that magnetic fields do not significantly increase the lifetime of cool clouds due to compression (in the case of tranverse fields) or the development of cloud tails (in the case of aligned fields), both of which promote mixing with the ambient medium (Cottle et al 2020). As both simulations evolve, we find an increasing lower limit of H I columns as well as a covering fraction of 100% for H I, both seen within ≈ 50 kpc.…”

Section: Kinematics and Ionsmentioning

confidence: 55%

“…The gas with β values 1 may be susceptible to magnetic draping, an effect in which a gas cloud moving through a magnetized plasma is able to rapidly build up a magnetic layer which may shield it from developing instabilities (e.g. Semenov & Bernikov 1980;Dursi & Pfrommer 2008;Cottle et al 2020). When looking at the quivers in Figure 9, we indeed see magnetic fields that have oriented themselves to be predominately parallel to the surface of the cool structures such as the extended central disk-like structure.…”

Section: Magnetic Fieldsmentioning

confidence: 92%

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Modeling Photoionized Turbulent Material in the Circumgalactic Medium

Buie

Gray

Scannapieco

2018

ApJ

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The circumgalactic medium (CGM) of nearby star-forming galaxies shows clear indications of O VI absorption accompanied by little to no detectable N V absorption. This unusual spectral signature, accompanied by highly non-uniform absorption from lower ionization state species, indicates that the CGM must be viewed as a dynamic, multiphase medium, such as occurs in the presence of turbulence. Motivated by previous isotropic turbulent simulations, we carry out chemodynamical simulations of stratified media in a Navarro-Frenk-White (NFW) gravitational potential with a total mass of 10 12 M and turbulence that decreases radially. The simulations assume a metallicity of 0.3 Z , a redshift zero metagalatic UV background, and they track ionizations, recombinations, and species-by-species radiative cooling using the MAIHEM package. We compare a suite of ionic column densities with the COS-Halos sample of low-redshift star-forming galaxies. Turbulence with an average onedimensional velocity dispersion ≈ 40 km s −1 , corresponding to an energy injection rate of ≈ 4 × 10 49 erg yr −1 , produces a CGM that matches many of the observed ionic column densities and ratios. In this simulation, the N N V /N O VI ratio is suppressed from its equilibrium value due to a combination of radiative cooling and cooling from turbulent mixing. This level of turbulence is consistent with expectations from observations of better constrained, highermass systems, and could be sustained by energy input from supernovae, gas inflows, and dynamical friction from dark matter subhalos. We also conduct a higher resolution ≈ 40 km s −1 run which yields smaller-scale structures, but remains in agreement with observations.

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Section: Kinematics and Ionsmentioning

confidence: 55%

Section: Magnetic Fieldsmentioning

confidence: 92%

Modeling Photoionized Turbulent Material in the Circumgalactic Medium

Buie

Gray

Scannapieco

2018

ApJ

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“…The parameter fKH reflects a combination of potential effects that could increase the longevity of cold clumps, such as very small-scale radiative cooling, magnetic field effects (e.g. McCourt et al (2015); Li et al (2019), though see Cottle et al (2020)), and the effects of a bulk outflow by which an entrained clump may experience a lower velocity relative to its surroundings than versus the ambient medium.…”

Section: Simulationsmentioning

confidence: 99%

A new model for including galactic winds in simulations of galaxy formation II: Implementation of PhEW in cosmological simulations

Huang

Katz

Cottle

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Although galactic winds play a critical role in regulating galaxy formation, hydrodynamic cosmological simulations do not resolve the scales that govern the interaction between winds and the ambient circumgalactic medium (CGM). We implement the Physically Evolved Wind (PhEW) model of Huang et al. (2020) in the gizmo hydrodynamics code and perform test cosmological simulations with different choices of model parameters and numerical resolution. PhEW adopts an explicit subgrid model that treats each wind particle as a collection of clouds that exchange mass and metals with their surroundings and evaporate by conduction and hydrodynamic instabilities as calibrated on much higher resolution cloud scale simulations. In contrast to a conventional wind algorithm, we find that PhEW results are robust to numerical resolution and implementation details because the small scale interactions are defined by the model itself. Compared to our previous wind simulations with the same resolution, our PhEW simulations are in better agreement with low-redshift galactic stellar mass functions at M* < 1011M⊙ because PhEW particles shed mass to the CGM before escaping low mass haloes. PhEW radically alters the CGM metal distribution because PhEW particles disperse metals to the ambient medium as their clouds dissipate, producing a CGM metallicity distribution that is skewed but unimodal and is similar between cold and hot gas. While the temperature distributions and radial profiles of gaseous haloes are similar in simulations with PhEW and conventional winds, these changes in metal distribution will affect their predicted UV/X-ray properties in absorption and emission.

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“…In contrast, later higher resolution simulations run with a variety of codes and numerical schemes (e.g. McCourt et al 2015;Banda-Barragán et al 2016;Grønnow et al 2017;Banda-Barragán et al 2018;Grønnow et al 2018;Cottle et al 2020;Gronke & Oh 2020a;Li et al 2020) have found that the magnetic field generally does not hasten the destruction. Instead, it tends to extend the overall cloud life time through its partial suppression of KH instability, although the effect is limited and often by itself insufficient to solve the problem of shorter than expected survival.…”

Section: Introductionmentioning

confidence: 98%

“…The general scenario of a cloud in relative motion with a surrounding hot magnetised medium has been widely studied in numerical simulations in the literature (e.g. Jones et al 1996;Gregori et al 1999Gregori et al , 2000Santillán et al 1999;Dursi & Pfrommer 2008;Kwak et al 2009;McCourt et al 2015;Banda-Barragán et al 2016;Grønnow et al 2017Grønnow et al , 2018Banda-Barragán et al 2018;Cottle et al 2020;Sparre et al 2020). In most of these simulations (the exceptions being Santillán et al 1999;Kwak et al 2009) there is no external gravitational potential and the cloud is instead given an initial velocity, either directly or, more commonly, by injecting a constant velocity 'wind' around it.…”

Section: Introductionmentioning

confidence: 99%

The role of the halo magnetic field on accretion through High-Velocity Clouds

Grønnow,

Tepper-García,

Bland-Hawthorn

et al. 2021

Preprint

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High-Velocity Clouds (HVCs) are believed to be an important source of gas accretion for star formation in the Milky Way. Earlier numerical studies have found that the Galactic magnetic field and radiative cooling strongly affects accretion. However, these effects have not previously been included together in the context of clouds falling through the Milky Way's gravitational potential. We explore this by simulating an initially stationary cloud falling through the hot hydrostatic corona towards the disc. This represents a HVC that has condensed out of the corona. We include the magnetic field in the corona to examine its effect on accretion of the HVC and its associated cold gas. Remnants of the original cloud survive in all cases, although a strong magnetic field causes it to split into several fragments. We find that mixing of cold and hot gas leads to cooling of coronal gas and an overall growth with time in cold gas mass, despite the low metallicity of the cloud and corona. The role of the magnetic field is to (moderately to severely) suppress the mixing and subsequent cooling, which in turn leads to less accretion compared to when the field is absent. A stronger field leads to less suppression of condensation because it enhances Rayleigh-Taylor instability. However, magnetic tension in a stronger field substantially decelerates condensed cloudlets. These have velocities typically a factor 3-8 below the velocity of the main cloud remnants by the end of the simulation. Some of these cloudlets likely disperse before reaching the disc.

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The Launching of Cold Clouds by Galaxy Outflows. III. The Influence of Magnetic Fields

Cited by 43 publications

References 68 publications

Modeling Photoionized Turbulent Material in the Circumgalactic Medium

Modeling Photoionized Turbulent Material in the Circumgalactic Medium

A new model for including galactic winds in simulations of galaxy formation II: Implementation of PhEW in cosmological simulations

The role of the halo magnetic field on accretion through High-Velocity Clouds

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