The density structure of supersonic self-gravitating turbulence

Abstract

We conduct numerical experiments to determine the density probability distribution function (PDF) produced in supersonic, isothermal, self-gravitating turbulence of the sort that is ubiquitous in star-forming molecular clouds. Our experiments cover a wide range of turbulent Mach number and virial parameter, allowing us for the first time to determine how the PDF responds as these parameters vary, and we introduce a new diagnostic, the dimensionless star formation efficiency versus density (${\epsilon }_{\mathrm{ff}}(s)$) curve, which provides a sensitive diagnostic of the PDF shape and dynamics. We show that the PDF follows a universal functional form consisting of a log-normal at low density with two distinct power law tails at higher density; the first of these represents the onset of self-gravitation, and the second reflects the onset of rotational support. Once the star formation efficiency reaches a few percent, the PDF becomes statistically steady, with no evidence for secular time-evolution at star formation efficiencies from about five to 20 percent. We show that both the Mach number and the virial parameter influence the characteristic densities at which the log-normal gives way to the first power-law, and the first to the second, and we extend (for the former) and develop (for the latter) simple theoretical models for the relationship between these density thresholds and the global properties of the turbulent medium.

18 pages, 10 figures, accepted in MNRAS, revised version

References in corpus (39)

• The Statistics of Supersonic Isothermal Turbulence
• 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
• On the Star Formation Efficiency of Turbulent Magnetized Clouds
• What determines the density structure of molecular clouds ? A case study of Orion B with Herschel
• On the Density Distribution in Star-forming Interstellar Clouds
• Inefficient star formation through turbulence, magnetic fields and feedback
• Numerical simulations of compressively driven interstellar turbulence: I. Isothermal gas
• The link between turbulence, magnetic fields, filaments, and star formation in the Central Molecular Zone cloud G0.253+0.016
• Fragmentation of Massive Protostellar Disks
• Modeling jet and outflow feedback during star cluster formation
• A robust numerical scheme for highly compressible magnetohydrodynamics: Nonlinear stability, implementation and tests
• Cloud Scale ISM Structure and Star Formation in M51
• The sonic scale revealed by the world's largest supersonic turbulence simulation
• Unfolding the Laws of Star Formation: The Density Distribution of Molecular Clouds
• A Direct Multigrid Poisson Solver for Oct-Tree Adaptive Meshes
• Molecular clouds have power-law probability distribution functions
• The Turbulent Warm Ionized Medium: Emission Measure Distribution and MHD Simulations
• Understanding star formation in molecular clouds I. Effects of line-of-sight contamination on the column density structure
• The density structure and star formation rate of non-isothermal polytropic turbulence
• Star Formation Relations in the Milky Way
• Density Probability Distribution Functions in Supersonic Hydrodynamic and MHD Turbulence
• Moving mesh simulations of star forming cores in magneto-gravo-turbulence
• Star Formation in Self-Gravitating Turbulent Fluids
• Understanding star formation in molecular clouds II. Signatures of gravitational collapse of IRDCs
• The shapes of column density PDFs - The importance of the last closed contour
• Density probability distribution functions of diffuse gas in the Milky Way
• The Razor's Edge of Collapse: The Transition Point from Lognormal to Powerlaw in Molecular Cloud PDFs
• Cloud Structure of Galactic OB Cluster Forming Regions from Combining Ground and Space Based Bolometric Observations
• On the Observed Diversity of Star Formation Efficiencies in Giant Molecular Clouds
• Evolution of the density PDF in star forming clouds: the role of gravity
• Relationship between turbulence energy and density variance in the Solar neighbourhood molecular clouds
• Density distribution function of a self-gravitating isothermal compressible turbulent fluid in the context of Molecular Clouds ensembles
• Implementation of stellar heating feedback in simulations of star cluster formation: effects on the initial mass function
• The Nature of Turbulence in the LITTLE THINGS Dwarf Irregular Galaxies
• Density distribution function of a self-gravitating isothermal compressible turbulent fluid in the context of Molecular Clouds ensembles II: the contribution of the turbulent term and the potential of the outer shells
• Turbulence and Star Formation in a Sample of Spiral Galaxies
• The turbulence driving parameter of molecular clouds in disc galaxies

Cited by in corpus (20)

• Understanding star formation in molecular clouds IV. Column density PDFs from quiescent to massive molecular clouds
• ALMA-IMF VI -- Investigating the origin of stellar masses: Core mass function evolution in the W43-MM2&MM3 mini-starburst
• The role of the turbulence driving mode for the Initial Mass Function
• First extragalactic measurement of the turbulence driving parameter: ALMA observations of the star-forming region N159E in the Large Magellanic Cloud
• A new method for spatially resolving the turbulence driving mixture in the ISM with application to the Small Magellanic Cloud
• The driving mode of shock-driven turbulence
• Playing with FIRE: A Galactic Feedback-Halting Experiment Challenges Star Formation Rate Theories
• The influence of the cloud virial parameter on the initial mass function
• Escaping the maze: a statistical sub-grid model for cloud-scale density structures in the interstellar medium
• Reconciling extragalactic star formation efficiencies with theory: insights from PHANGS
• Multi log-normal density structure in Cygnus-X molecular clouds: A fitting for N-PDF without power-law
• A two-phase model of galaxy formation: III. The formation of globular clusters
• Density Exponent Analysis: Gravity-driven steepening of the density profiles of star-forming regions
• Density distribution function of a self-gravitating isothermal turbulent fluid in the context of molecular clouds ensembles -- III. Virial analysis
• Structure of iso-density sets in supersonic isothermal turbulence
• Recovering the properties of the interstellar medium through integrated spectroscopy: application to the z~0 ECO volume-limited star-forming galaxy sample
• CO mapping of Cygnus-X -- volume density distribution
• Impact of the shape of the prestellar density fluctuations on the core mass function
• Sub-kpc scale gas density histogram of the Galactic molecular gas: a new statistical method to characterise galactic-scale gas structures
• Contour Analysis Tool: an interactive tool for background and morphology analysis