Isothermal Fragmentation: Is there a low-mass cut-off?

Abstract

The evolution of self-gravitating clouds of isothermal gas forms the basis of many star formation theories. Therefore it is important to know under what conditions such a cloud will undergo homologous collapse into a single, massive object, or will fragment into a spectrum of smaller ones. And if it fragments, do initial conditions (e.g. Jeans mass, sonic mass) influence the mass function of the fragments, as predicted by many theories of star formation? In this paper we show that the relevant parameter separating homologous collapse from fragmentation is not the Mach number of the initial turbulence (as suspected by many), but the infall Mach number ${\mathcal{M}}_{\mathrm{infall}}\sim \sqrt{GM/(R{c}_s^2)}$, equivalent to the number of Jeans masses in the initial cloud $N_J$. We also show that fragmenting clouds produce a power-law mass function with slopes close to the expected -2 (i.e. equal mass in all logarithmic mass intervals). However, the low-mass cut-off of this mass function is entirely numerical; the initial properties of the cloud have no effect on it. In other words, if ${\mathcal{M}}_{\mathrm{infall}}\gg 1$, fragmentation proceeds without limit to masses much smaller than the initial Jeans mass.

10 pages, 9 figures

References in corpus (14)

• Theory of Star Formation
• Analytical theory for the initial mass function: CO clumps and prestellar cores
• The Density Probability Distribution in Compressible Isothermal Turbulence: Solenoidal versus Compressive Forcing
• Modeling Collapse and Accretion in Turbulent Gas Clouds: Implementation and Comparison of Sink Particles in AMR and SPH
• Numerical simulations of compressively driven interstellar turbulence: I. Isothermal gas
• Cooling, Gravity and Geometry: Flow-driven Massive Core Formation
• On the nature of star-forming filaments: I. Filament morphologies
• The formation of molecular clouds in spiral galaxies
• The Jeans mass and the origin of the knee in the IMF
• The stellar IMF from Isothermal MHD Turbulence
• Stellar mass spectrum within massive collapsing clumps II. Thermodynamics and tidal forces of the first Larson core
• Protostar Formation in Supersonic Flows: Growth and Collapse of Spherical Cores
• Bondi-Hoyle-Littleton accretion and the upper mass stellar IMF
• Prestellar Core Formation, Evolution, and Accretion from Gravitational Fragmentation in Turbulent Converging Flows

Cited by in corpus (36)

• Global Hierarchical Collapse In Molecular Clouds. Towards a Comprehensive Scenario
• STARFORGE: Toward a comprehensive numerical model of star cluster formation and feedback
• The dynamics and outcome of star formation with jets, radiation, winds, and supernovae in concert
• Preliminary Trigonometric Parallaxes of 184 Late-T and Y Dwarfs and an Analysis of the Field Substellar Mass Function into the "Planetary" Mass Regime
• Transition of the initial mass function in the metal-poor environments
• STARFORGE: The effects of protostellar outflows on the IMF
• Effects of the environment and feedback physics on the initial mass function of stars in the STARFORGE simulations
• On The Nature of Variations in the Measured Star Formation Efficiency of Molecular Clouds
• Does the magnetic field suppress fragmentation in massive dense cores?
• Outflows Driven by Direct and Reprocessed Radiation Pressure in Massive Star Clusters
• The Origin of the Stellar Mass Distribution and Multiplicity
• The Maximum Stellar Surface Density Due to the Failure of Stellar Feedback
• The IMF and multiplicity of stars from gravity, turbulence, magnetic fields, radiation and outflow feedback
• Density profile evolution during prestellar core collapse: Collapse starts at the large scale
• Can magnetized turbulence set the mass scale of stars?
• Mixing of metals during star cluster formation: statistics and implications for chemical tagging
• Multi-scale dynamics in star-forming regions: the interplay between gravity and turbulence
• The Supersonic Project: Shining Light on SIGOs - a New Formation Channel for Globular Clusters
• The Elephant in the Room: The Importance of Where and When Massive Stars Form in Molecular Clouds
• Stellar mass spectrum within massive collapsing clumps III. Effects of temperature and magnetic field
• The role of initial magnetic field structure in the launching of protostellar jets
• The role of the turbulence driving mode for the Initial Mass Function
• An ablating super-Earth in an eccentric binary from the Dispersed Matter Planet Project
• Hyper-Eddington Black Hole Growth in Star-Forming Molecular Clouds and Galactic Nuclei: Can It Happen?
• On the origin of the peak of the stellar initial mass function: exploring the tidal screening theory
• The role of turbulence during the formation of circumbinary discs
• A general-purpose timestep criterion for simulations with gravity
• The Supersonic Project: To cool or not to cool Supersonically Induced Gas Objects (SIGOs)?
• Environmental variation of the low-mass IMF
• Role of magnetic fields in the formation of direct collapse black holes
• Novel Conservative Methods for Adaptive Force Softening in Collisionless and Multi-Species N-Body Simulations
• A graph theory-based multi-scale analysis of hierarchical cascade in molecular clouds : Application to the NGC 2264 region
• A stochastic and analytical model of hierarchical fragmentation: The fragmentation of gas structures into young stellar objects in the interstellar medium
• Prestellar Cores in Turbulent Clouds: Properties of Critical Cores
• When did the initial mass function become bottom-heavy?
• Star Formation