Can magnetized turbulence set the mass scale of stars?

2020/02/29 by David Guszejnov, Dávid Guszejnov, Michael Y Grudić +5
Chemical Engineering · Physics and Astronomy · #Advanced Combustion Engine Technologies #Astrophysics #Astrophysics and Star Formation Studies #Galaxy #Initial mass function #Magnetic field #Magnetohydrodynamics #Molecular cloud #Order (exchange) #Physics #Quantum mechanics #Star formation #Stars #Stellar mass #Stellar, planetary, and galactic studies #Virial theorem #astro-ph.GA

paper · pdf · doi:10.1093/mnras/staa1883

Note that this version has erratum at the end (does not affect results) 18 pages, 17 figures

openalex publication_date 2020/06/29 · arxiv created 2020/10/26 · arxiv updated 2020/10/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06

Abstract

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 ∼ 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 M₅0 \buildrel∝ \over ∼ M₀ \mathcal M^-3 α _turb 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 \gt 20 M_\odot , an order of magnitude larger than observed (∼ 2 M_\odot), 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.

Citations

• The stellar initial mass function, core mass function and the last-crossing distribution
• The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems
• Physical Models of Galaxy Formation in a Cosmological Framework
• From filamentary clouds to prestellar cores to the stellar IMF: Initial highlights from theHerschelGould Belt Survey
• Starburst99: Synthesis Models for Galaxies with Active Star Formation
• Mach Number Dependence of Turbulent Magnetic Field Amplification: Solenoidal versus Compressive Flows
• Problems of Gravitational Stability in the Presence of a Magnetic Field.
• Dissipation in Compressible Magnetohydrodynamic Turbulence
• THE TURBULENT DYNAMO IN HIGHLY COMPRESSIBLE SUPERSONIC PLASMAS
• The Formation of Massive Stars from Turbulent Cores
• Star Formation in Molecular Clouds: Observation and Theory
• The impact of magnetic fields on single and binary star formation
• The necessity of feedback physics in setting the peak of the initial mass function
• Magnetic Fields in Molecular Clouds
• Does turbulence determine the initial mass function?
• The Stellar IMF from Isothermal MHD Turbulence
• Stellar mass spectrum within massive collapsing clumps
• STARFORGE: Towards a comprehensive numerical model of star cluster formation and feedback
• Stellar mass spectrum within massive collapsing clumps