Virialization of the Inner CGM in the FIRE Simulations and Implications for Galaxy Disks, Star Formation, and Feedback

Stern, Jonathan; Faucher-Giguère, Claude-André; Fielding, Drummond B.; Quataert, Eliot; Hafen, Zachary; Gurvich, Alexander B.; Ma, Xiangcheng; Byrne, Lindsey; El-Badry, Kareem; Anglés-Alcázar, Daniel; Chan, T. K.; Feldmann, Robert; Kereš, Dušan; Wetzel, Andrew; Murray, Norman; Hopkins, Philip F.

doi:10.3847/1538-4357/abd776

Cited by 97 publications

(83 citation statements)

References 123 publications

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“…The qualitative effects are similar to our m12i case study, albeit weaker. In MHD+, we see that while slightly lower mass 10 11 M haloes have rapidly dropping t cool inside R vir , these haloes are indeed beginning to building up 'hot halo', with high central temperatures and t cool ∼ 5 t inflow ∼ 10 t ff for the hot volume-filling phase at outer CGM radii (at inner CGM radii gas remains cool, in 10 11 − 10 12 M haloes, see Stern et al 2020), and (as a consequence) a visible quasi-spherical virial shock emerges. In CR+, the combination of larger t inflow and lower t cool keeps t cool ∼ t inflow at r ࣠ R vir .…”

Section: Halo Massmentioning

confidence: 85%

“…'hot halo') solution (see e.g. Stern et al 2020), for more discussion of these solutions in our non-CR runs).…”

Section: Inflowsmentioning

confidence: 99%

“…Ocvirk, Pichon & Teyssier 2008;Brooks et al 2009;Kereš & Hernquist 2009;Oppenheimer et al 2010;Faucher-Giguère, Kereš & Ma 2011;van de Voort et al 2011;Nelson et al 2013), and how galactic feedback from stars or AGN and hydrodynamic instabilities affect this transition (e.g. Kereš & Hernquist 2009;Faucher-Giguere et al 2015Fielding et al 2017;Nelson et al 2019;Esmerian et al 2020;Stern et al 2020).…”

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confidence: 99%

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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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Section: Halo Massmentioning

confidence: 85%

“…'hot halo') solution (see e.g. Stern et al 2020), for more discussion of these solutions in our non-CR runs).…”

Section: Inflowsmentioning

confidence: 99%

mentioning

confidence: 99%

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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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“…Kere š et al 2005 ). Additionally, simulations found that gas can accrete in 'cold-mode', along filamentary streams, where gas does not shock to the virial temperature in the outer halo (Kere š et al 2005 ;Dekel & Birnboim 2006 ;Ocvirk, Pichon & Teyssier 2008 ;Brooks et al 2009 ; ; Faucher-Gigu ère, Kere š & Ma 2011 ; van de Voort et al 2011a ;Stern et al 2021 ). Such accretion dominates at early times, while at late times and/or in more massive haloes cooling from the hot halo gas ('hot-mode') can be more important.…”

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confidence: 99%

Gas infall and radial transport in cosmological simulations of milky way-mass discs

Trapp

Kereš

Chan

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Observations indicate that a continuous supply of gas is needed to maintain observed star formation rates in large, disky galaxies. To fuel star formation, gas must reach the inner regions of such galaxies. Despite its crucial importance for galaxy evolution, how and where gas joins galaxies is poorly constrained observationally and rarely explored in fully cosmological simulations. To investigate gas accretion in the vicinity of galaxies at low redshift, we analyse the FIRE-2 cosmological zoom-in simulations for 4 Milky Way mass galaxies (Mhalo ∼ 1012M⊙), focusing on simulations with cosmic ray physics. We find that at z ∼ 0, gas approaches the disk with angular momentum similar to the gaseous disk edge and low radial velocities, piling-up near the edge and settling into full rotational support. Accreting gas moves predominately parallel to the disk and joins largely in the outskirts. Immediately prior to joining the disk, trajectories briefly become more vertical on average. Within the disk, gas motion is complex, being dominated by spiral arm induced oscillations and feedback. However, time and azimuthal averages show slow net radial infall with transport speeds of 1-3 km s−1 and net mass fluxes through the disk of ∼M⊙ yr−1, comparable to the galaxies’ star formation rates and decreasing towards galactic center as gas is sunk into star formation. These rates are slightly higher in simulations without cosmic rays (1-7 km s−1, ∼4-5 M⊙ yr−1). We find overall consistency of our results with observational constraints and discuss prospects of future observations of gas flows in and around galaxies.

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“…Agertz & Kravtsov 2016) and the way in which gas is accreted and lost in feedback driven outflows. Yu et al (2021) used cosmological simulations of Milky Way-mass galaxies to show that thin galactic discs cannot form unless the gas cooling time in the circum-galactic medium (CGM) is longer than the dynamical time (see also Stern et al 2021). The authors argued that for short CGM cooling times, gas is accreted more rapidly, leading to burstier star formation and thick disc formation.…”

Section: Discussionmentioning

confidence: 99%

From giant clumps to clouds -- II. The emergence of thick disc kinematics from the conditions of star formation in high redshift gas rich galaxies

van Donkelaar,

Agertz,

Renaud

2021

Preprint

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High redshift disc galaxies are more gas rich, clumpier, and more turbulent than local Universe galaxies. This early era of galaxy formation imprints the distribution and kinematics of the stars that we observe today, but it is not yet well established how. In this work, we use simulations of isolated Milky Way-mass disc galaxies to study how kinematic properties of stars change when varying the gas fraction. This allows us to quantify the roles played by internal processes, e.g. gas turbulence and gravitational scattering off massive gas clumps, in establishing the observed stellar velocity dispersions and orbital eccentricities. We find that models with gas fractions > 20 per cent feature a turbulent and clumpy interstellar medium (ISM), leading to zero-age stellar velocity dispersions ∼ 20 − 30 km s −1 and high mean orbital eccentricities. Low eccentricities cannot arise from these physical conditions. For gas fractions below 20 per cent, the ISM becomes less turbulent, with stellar velocity dispersions < 10 km s −1 , and nearly circular orbits for young stars. The turbulence present in gas-rich high redshift galaxies hence acts as a 'barrier' against the formation of thin discs. We compare our findings to the Milky Way's age-velocity dispersion relation and argue that velocity dispersions imprinted already at star formation by the ISM contribute significantly at all times. Finally, we show that observed orbital eccentricities in the Milky Way's thick and thin discs can be explained entirely as imprints by the star-forming ISM, rather than by mergers or secular processes.

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Virialization of the Inner CGM in the FIRE Simulations and Implications for Galaxy Disks, Star Formation, and Feedback

Cited by 97 publications

References 123 publications

Virial shocks are suppressed in cosmic ray-dominated galaxy haloes

Virial shocks are suppressed in cosmic ray-dominated galaxy haloes

Gas infall and radial transport in cosmological simulations of milky way-mass discs

From giant clumps to clouds -- II. The emergence of thick disc kinematics from the conditions of star formation in high redshift gas rich galaxies

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