Can magnetized turbulence set the mass scale of stars?

Guszejnov, Dávid; Grudić, Michael Y.; Hopkins, Philip F.; Offner, Stella S. R.; Faucher-Giguère, Claude-André

doi:10.1093/mnras/staa1883

Cited by 42 publications

(44 citation statements)

References 130 publications

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“…The field strength is not as high in our simulation because the field is quenched as a result of the limited resolution for a minimum cell size of 4 AU, and turbulence hampers the pile-up of the magnetic field in our model, similar to the recent results by Guszejnov et al (2020). If we resolved the vicinity of the young star in more detail, we would reach higher densities and higher magnetic field strengths as a consequence of flux-freezing.…”

Section: Distribution Of the B-field Strengthsupporting

confidence: 74%

Linear dust polarization during the embedded phase of protostar formation

Küffmeier

Reißl

Wolf

et al. 2020

A&A

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Context. Measuring polarization from thermal dust emission can provide important constraints on the magnetic field structure around embedded protostars. However, interpreting the observations is challenging without models that consistently account for both the complexity of the turbulent protostellar birth environment and polarization mechanisms. Aims. We aim to provide a better understanding of dust polarization maps of embedded protostars with a focus on bridge-like structures such as the structure observed toward the protostellar multiple system IRAS 16293–2422 by comparing synthetic polarization maps of thermal reemission with recent observations. Methods. We analyzed the magnetic field morphology and properties associated with the formation of a protostellar multiple based on ideal magnetohydrodynamic 3D zoom-in simulations carried out with the RAMSES code. To compare the models with observations, we postprocessed a snapshot of a bridge-like structure that is associated with a forming triple star system with the radiative transfer code POLARIS and produced multiwavelength dust polarization maps. Results. The typical density in the most prominent bridge of our sample is about 10−16 g cm−3, and the magnetic field strength in the bridge is about 1 to 2 mG. Inside the bridge, the magnetic field structure has an elongated toroidal morphology, and the dust polarization maps trace the complex morphology. In contrast, the magnetic field strength associated with the launching of asymmetric bipolar outflows is significantly more magnetized (~100 mG). At λ = 1.3 mm, and the orientation of the grains in the bridge is very similar for the case accounting for radiative alignment torques (RATs) compared to perfect alignment with magnetic field lines. However, the polarization fraction in the bridge is three times smaller for the RAT scenario than when perfect alignment is assumed. At shorter wavelength (λ ≲ 200 μm), however, dust polarization does not trace the magnetic field because other effects such as self-scattering and dichroic extinction dominate the orientation of the polarization. Conclusions. Compared to the launching region of protostellar outflows, the magnetic field in bridge-like structures is weak. Synthetic dust polarization maps of ALMA Bands 6 and 7 (1.3 mm and 870 μm, respectively) can be used as a tracer of the complex morphology of elongated toroidal magnetic fields associated with bridges.

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Section: Distribution Of the B-field Strengthsupporting

confidence: 74%

Linear dust polarization during the embedded phase of protostar formation

Küffmeier

Reißl

Wolf

et al. 2020

A&A

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“…the mean stellar mass is ∼4 M in the simulations, while ∼0.4 M is observed). This study also found that stellar masses in isothermal magnetohydrodynamics (MHD) also increase with time and are sensitive to initial conditions (ICs; see analysis in section 4.2 of Guszejnov et al 2020), leading to order of magnitude variations in the predicted characteristic scale of the IMF. Observations, however, have found the IMF to be near-universal within the MW, with variations in the IMF peak mass within a factor of <3 (see reviews of Bastian, Covey &Meyer 2010 and, as well as analysis of Dib 2014).…”

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confidence: 61%

“…Padoan et al 2007;Padoan & Nordlund 2011;Haugbølle, Padoan & Nordlund 2018). While some of these studies claimed to reproduce the observed initial mass function (IMF), our recent study (Guszejnov et al 2020) showed that, for clouds similar to giant molecular clouds (GMCs) in the Milky Way (MW), the mean stellar masses predicted by these magnetized, gravoturbulent models are an order of magnitude higher than observed (i.e. the mean stellar mass is ∼4 M in the simulations, while ∼0.4 M is observed).…”

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confidence: 85%

“…Similar to our previous studies of isothermal collapse with and without magnetic fields (Guszejnov et al 2018b andGuszejnov et al 2020, to the latter of which we will henceforth refer to as Paper 0), we simulate star-forming clouds with the GIZMO code 2 (Hopkins 2015), using the Lagrangian meshless finite-mass method for MHD (Hopkins & Raives 2016), assuming ideal MHD (with the constrained gradient scheme of Hopkins 2016 to ensure that…”

Section: Core Physicsmentioning

confidence: 99%

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STARFORGE: the effects of protostellar outflows on the IMF

Guszejnov

Grudić

Hopkins

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The initial mass function (IMF) of stars is a key quantity affecting almost every field of astrophysics, yet it remains unclear what physical mechanisms determine it. We present the first runs of the STARFORGE project, using a new numerical framework to follow the formation of individual stars in giant molecular clouds (GMCs) using the GIZMO code. Our suite includes runs with increasingly complex physics, starting with isothermal ideal magnetohydrodynamics (MHD) and then adding non-isothermal thermodynamics and protostellar outflows. We show that without protostellar outflows the resulting stellar masses are an order of magnitude too high, similar to the result in the base isothermal MHD run. Outflows disrupt the accretion flow around the protostar, allowing gas to fragment and additional stars to form, thereby lowering the mean stellar mass to a value similar to that observed. The effect of jets upon global cloud evolution is most pronounced for lower-mass GMCs and dense clumps, so while jets can disrupt low-mass clouds, they are unable to regulate star formation in massive GMCs, as they would turn an order unity fraction of the mass into stars before unbinding the cloud. Jets are also unable to stop the runaway accretion of massive stars, which could ultimately lead to the formation of stars with masses >500 M⊙. Although we find that the mass scale set by jets is insensitive to most cloud parameters (i.e., surface density, virial parameter), it is strongly dependent on the momentum loading of the jets (which is poorly constrained by observations) as well the the temperature of the parent cloud, which predicts slightly larger IMF variations than observed. We conclude that protostellar jets play a vital role in setting the mass scale of stars, but additional physics are necessary to reproduce the observed IMF.

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“…Cooling physics for large dynamic range: Our cooling module includes dust-gas thermal coupling, cosmic raygas coupling, and a treatment for optically thick cooling, which is crucial to capture the thermodynamic state of gas at the densities reached in the nuclear disk (n H > 10 7 cm −3 ). The same cooling physics has been used for individual molecular cloud-scale simulations (Grudić et al 2018;Guszejnov et al 2020) reaching 10 −5 pc resolution. 8.…”

Section: Discussionmentioning

confidence: 99%

Cosmological Simulations of Quasar Fueling to Subparsec Scales Using Lagrangian Hyper-refinement

Anglés-Alcázar

Quataert

Hopkins

et al. 2021

ApJ

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We present cosmological hydrodynamic simulations of a quasar-mass halo (M halo ≈ 10 12.5 M e at z = 2) that for the first time resolve gas transport down to the inner 0.1 pc surrounding the central massive black hole. We model a multiphase interstellar medium including stellar feedback by supernovae, stellar winds, and radiation, and a hyper-Lagrangian refinement technique increasing the resolution dynamically approaching the black hole. We do not include black hole feedback. We show that the subpc inflow rate (1) can reach ∼6 M e yr −1 roughly in steady state during the epoch of peak nuclear gas density (z ∼ 2), sufficient to power a luminous quasar, (2) is highly time variable in the pre-quasar phase, spanning 0.001-10 M e yr −1 on Myr timescales, and (3) is limited to short (∼2 Myr) active phases (0.01-0.1 M e yr −1 ) followed by longer periods of inactivity at lower nuclear gas density and late times (z ∼ 1), owing to the formation of a hot central cavity. Inflowing gas is primarily cool, rotational support dominates over turbulence and thermal pressure, and star formation can consume as much gas as provided by inflows across 1 pc-10 kpc. Gravitational torques from multiscale stellar non-axisymmetries dominate angular momentum transport over gas self-torquing and pressure gradients, with accretion weakly dependent on black hole mass. Subpc inflow rates correlate with nuclear (but decouple from global) star formation and can exceed the Eddington rate by ×10. The black hole can move ∼10 pc from the galaxy center on ∼0.1 Myr. Accreting gas forms pc-scale, rotationally supported, obscuring structures often misaligned with the galaxy-scale disk. These simulations open a new avenue to investigate black hole-galaxy coevolution.

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Can magnetized turbulence set the mass scale of stars?

Cited by 42 publications

References 130 publications

Linear dust polarization during the embedded phase of protostar formation

Linear dust polarization during the embedded phase of protostar formation

STARFORGE: the effects of protostellar outflows on the IMF

Cosmological Simulations of Quasar Fueling to Subparsec Scales Using Lagrangian Hyper-refinement

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