Evolution of giant molecular clouds across cosmic time

Guszejnov, Dávid; Grudić, Michael Y.; Offner, Stella S. R.; Boylan-Kolchin, Michael; Faucher-Gigère, Claude-André; Wetzel, Andrew; Benincasa, Samantha M.; Loebman, Sarah

doi:10.1093/mnras/stz3527

Cited by 55 publications

(54 citation statements)

References 84 publications

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“…For α turb ∼ 1, this is simply the criterion that the sonic mass (Equation 15) or turbulent Bonnor-Ebert mass (Equation 16) be resolved by 20∆m. These are both proposed characteristic core masses in turbulent fragmentation (Padoan et al 2007;Hopkins 2012), and the specific number is on the order of the minimum number of Lagrangian mass elements for the stability of a clump to be insensitive to numerical discretization and softening details (Bate et al 1995;Price & Monaghan 2007, Grudić et al 2020. Thus Equation 22 simply expresses the requirement that the collapse of gravitationally-unstable cores formed via turbulent fragmentation is sufficiently resolved.…”

Section: Resolution Insensitivity Of the Characteristic Massmentioning

confidence: 99%

“…However, their effect upon the IMF must be indirect, because they occur too late to significantly affect the evolution of dense clumps in which star clusters form. Their main role in star formation is likely maintaining the state of ISM turbulence on the scale of the galactic scale height and driving galactic outflows (via super-bubbles and chimneys), thus regulating the ISM gas densities and other "environmental" properties which set the properties of GMCs in turn (e.g., Hopkins et al 2011Hopkins et al , 2012Walch et al 2015;Padoan et al 2017;Seifried et al 2018;Guszejnov et al 2020).…”

Section: The Necessity Of Feedback Regulationmentioning

confidence: 99%

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Can magnetized turbulence set the mass scale of stars?

Guszejnov

Grudić

Hopkins

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Abstract Understanding the evolution of self-gravitating, isothermal, magnetized gas is crucial for star formation, as these physical processes have been postulated to set the initial mass function (IMF). We present a suite of isothermal magnetohydrodynamic (MHD) simulations using the GIZMO code, that follow the formation of individual stars in giant molecular clouds (GMCs), spanning a range of Mach numbers found in observed GMCs ($\mathcal {M} \sim 10-50$). As in past works, the mean and median stellar masses are sensitive to numerical resolution, because they are sensitive to low-mass stars that contribute a vanishing fraction of the overall stellar mass. The mass-weighted median stellar mass M50 becomes insensitive to resolution once turbulent fragmentation is well-resolved. Without imposing Larson-like scaling laws, our simulations find $M_\mathrm{50} M_\mathrm{0} \mathcal {M}^{-3} \alpha _\mathrm{turb} \mathrm{SFE}^{1/3}$ for GMC mass M0, sonic Mach number $\mathcal {M}$, virial parameter αturb, and star formation efficiency SFE = M⋆/M0. This fit agrees well with previous IMF results from the RAMSES, ORION2, and SphNG codes. Although M50 has no significant dependence on the magnetic field strength at the cloud scale, MHD is necessary to prevent a fragmentation cascade that results in non-convergent stellar masses. For initial conditions and SFE similar to star-forming GMCs in our Galaxy, we predict M50 to be >20M⊙, an order of magnitude larger than observed (∼2M⊙), together with an excess of brown dwarfs. Moreover, M50 is sensitive to initial cloud properties and evolves strongly in time within a given cloud, predicting much larger IMF variations than are observationally allowed. We conclude that physics beyond MHD turbulence and gravity are necessary ingredients for the IMF.

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Section: Resolution Insensitivity Of the Characteristic Massmentioning

confidence: 99%

Section: The Necessity Of Feedback Regulationmentioning

confidence: 99%

Can magnetized turbulence set the mass scale of stars?

Guszejnov

Grudić

Hopkins

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…ies (Sanderson et al 2018;Orr et al 2018;El-Badry et al 2018b,a;Hung et al 2019;Guszejnov et al 2019).…”

Section: Methodsunclassified

Live fast, die young: GMC lifetimes in the FIRE cosmological simulations of Milky Way mass galaxies

Benincasa

Loebman

Wetzel

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present the first measurement of the lifetimes of Giant Molecular Clouds (GMCs) in cosmological simulations at z = 0, using the Latte suite of FIRE-2 simulations of Milky Way-mass galaxies. We track GMCs with total gas mass ≳ 105 M⊙ at high spatial (∼1 pc), mass (7100 M⊙), and temporal (1 Myr) resolution. Our simulated GMCs are consistent with the distribution of masses for massive GMCs in the Milky Way and nearby galaxies. We find GMC lifetimes of 5 − 7 Myr, or 1-2 freefall times, on average, with less than 2% of clouds living longer than 20 Myr. We find decreasing GMC lifetimes with increasing virial parameter, and weakly increasing GMC lifetimes with galactocentric radius, implying that environment affects the evolutionary cycle of GMCs. However, our GMC lifetimes show no systematic dependence on GMC mass or amount of star formation. These results are broadly consistent with inferences from the literature and provide an initial investigation into ultimately understanding the physical processes that govern GMC lifetimes in a cosmological setting.

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“…giant molecular clouds (Benincasa et al 2019a;Guszejnov et al 2020), and the KS relation (Orr et al 2018).…”

Section: This Papermentioning

confidence: 99%

Pressure balance in the multiphase ISM of cosmologically simulated disc galaxies

Gurvich

Faucher-Giguère

Richings

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Pressure balance plays a central role in models of the interstellar medium (ISM), but whether and how pressure balance is realized in a realistic multiphase ISM is not yet well understood. We address this question using a set of FIRE-2 cosmological zoom-in simulations of Milky Way-mass disk galaxies, in which a multiphase ISM is self-consistently shaped by gravity, cooling, and stellar feedback. We analyze how gravity determines the vertical pressure profile as well as how the total ISM pressure is partitioned between different phases and components (thermal, dispersion/turbulence, and bulk flows). We show that, on average and consistent with previous more idealized simulations, the total ISM pressure balances the weight of the overlying gas. Deviations from vertical pressure balance increase with increasing galactocentric radius and with decreasing averaging scale. The different phases are in rough total pressure equilibrium with one another, but with large deviations from thermal pressure equilibrium owing to kinetic support in the cold and warm phases, which dominate the total pressure near the midplane. Bulk flows (e.g., inflows and fountains) are important at a few disk scale heights, while thermal pressure from hot gas dominates at larger heights. Overall, the total midplane pressure is well-predicted by the weight of the disk gas, and we show that it also scales linearly with the star formation rate surface density (ΣSFR). These results support the notion that the Kennicutt-Schmidt relation arises because ΣSFR and the gas surface density (Σg) are connected via the ISM midplane pressure.

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Evolution of giant molecular clouds across cosmic time

Cited by 55 publications

References 84 publications

Can magnetized turbulence set the mass scale of stars?

Can magnetized turbulence set the mass scale of stars?

Live fast, die young: GMC lifetimes in the FIRE cosmological simulations of Milky Way mass galaxies

Pressure balance in the multiphase ISM of cosmologically simulated disc galaxies

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