Energy budget of forming clumps in numerical simulations of collapsing clouds

Abstract

We analyze the physical properties and energy balance of density enhancements in two SPH simulations of the formation, evolution, and collapse of giant molecular clouds. In the simulations, no feedback is included, so all motions are due either to the initial, decaying turbulence, or to gravitational contraction. We define clumps as connected regions above a series of density thresholds. The resultingfull set of clumps follows the generalized energy-equipartition relation ${\sigma }_v/R^{1/2}\propto {\Sigma }^{1/2}$, where ${\sigma }_v$ is the velocity dispersion, $R$ is the "radius", and $\Sigma$ is the column density. We interpret this as a natural consequence of gravitational contraction at all scales, rather than virial equilibrium. Nevertheless, clumps with low $\Sigma$ tend to show a large scatter around equipartition. In more than half of the cases, this scatter is dominated by external turbulent compressions that {\it assemble} the clumps, rather than by small-scale random motions that would disperse them. The other half does actually disperse. Moreover, clump sub-samples selected by means of different criteria exhibit different scalings. Sub-samples with narrow $\Sigma$ ranges follow Larson-like relations, although characterized by their respective value of $\Sigma$. Finally, we find that: i) clumps lying in filaments tend to appear sub-virial; ii) high-density cores ($n\ge 10^5$ cm${}^3$) that exhibit moderate kinetic energy excesses often contain sink ("stellar") particles, and the excess disappears when the stellar mass is taken into account in the energy balance; iii) cores with kinetic energy excess but no stellar particles are truly in a state of dispersal.

arXiv commentAbstract rephrased. Submitted to ApJ

References in corpus (66)

• Embedded Clusters in Molecular Clouds
• Theory of Star Formation
• GADGET: A code for collisionless and gasdynamical cosmological simulations
• Interstellar Turbulence I: Observations and Processes
• Re-examining Larson's Scaling Relationships in Galactic Molecular Clouds
• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• The Universality of Turbulence in Galactic Molecular Clouds
• Efficiencies of Low-Mass Star and Star Cluster Formation
• Molecular Cloud Evolution II. From cloud formation to the early stages of star formation in decaying conditions
• Global collapse of molecular clouds as a formation mechanism for the most massive stars
• An Origin of Supersonic Motions in Interstellar Clouds
• Dynamic star formation in the massive DR21 filament
• Thermal condensation in a turbulent atomic hydrogen flow
• Filamentary Accretion Flows in the Embedded Serpens South Protocluster
• The Equilibrium State of Molecular Regions in the Outer Galaxy
• The stellar mass spectrum from non-isothermal gravoturbulent fragmentation
• Massive stars in massive clusters II: Disruption of bound clusters by photoionization
• Accretion-Driven Turbulence as Universal Process: Galaxies, Molecular Clouds, and Protostellar Disks
• Dense Gas and Star Formation: Characteristics of Cloud Cores Associated with Water Masers
• Protostellar Turbulence Driven by Collimated Outflows
• Gravity or Turbulence? The velocity dispersion-size relation
• Molecular cloud evolution. I. Molecular cloud and thin CNM sheet formation
• The Properties of Massive, Dense, Clumps: Mapping Surveys of HCN and CS
• From the warm magnetized atomic medium to molecular clouds
• Stellar Feedback in Molecular Clouds and its Influence on the Mass Function of Young Star Clusters
• ALMA Reveals the Molecular Medium Fueling the Nearest Nuclear Starburst
• Kinetic and Structural Evolution of Self-gravitating, Magnetized Clouds: 2.5-Dimensional Simulations of Decaying Turbulence
• The Birth of Molecular Clouds: Formation of Atomic Precursors in Colliding Flows
• A CS J=5-4 Mapping Survey Towards High-mass Star Forming Cores Associated with Water Masers
• Supernova Driving. I. The Origin of Molecular Cloud Turbulence
• Cooling, Gravity and Geometry: Flow-driven Massive Core Formation
• Formation of Structure in Molecular Clouds: A Case Study
• Physical vs. Observational Properties of Clouds in Turbulent Molecular Cloud Models
• Filaments in Simulations of Molecular Cloud Formation
• Why are most molecular clouds not gravitationally bound?
• Modelling the supernova-driven ISM in different environments
• Rapid Molecular Cloud and Star Formation: Mechanisms and Movies
• High- and Low-Mass Star Forming Regions from Hierarchical Gravitational Fragmentation. High local Star Formation Rates with Low Global Efficiencies
• Molecular clouds have power-law probability distribution functions
• Larson's third law and the universality of molecular cloud structure
• Molecular Cloud Evolution III. Accretion vs. stellar feedback
• A Search for Larson-Type Relations in Numerical Simulations of the ISM. Evidence for Non-Constant Column Densities
• Is Thermal Instability Significant in Turbulent Galactic Gas?
• Early stages of cluster formation: fragmentation of massive dense cores down to ~1000 AU
• Molecular Cloud Evolution V. Cloud Destruction by Stellar Feedback
• Gravitational contraction versus Supernova driving and the origin of the velocity dispersion-size relation in molecular clouds
• Aspect Ratio Dependence of the Free-Fall Time for Non-Spherical Symmetries
• Does External Pressure Explain Recent Results for Molecular Clouds?
• The Nature of the Velocity Field in Molecular Clouds. I. The Non-Magnetic Case
• An Evolutionary Model for Collapsing Molecular Clouds and Their Star Formation Activity
• Star Formation Efficiency in Driven, Supercritical, Turbulent Clouds
• The W43-MM1 mini-starburst ridge, a test for star formation efficiency models
• The Galactic Census of High- and Medium-mass Protostars. I. Catalogues and First Results from Mopra HCO+ Maps
• The Free-Fall time of finite Sheets and Filaments
• rpSPH: a novel Smoothed Particle Hydrodynamics Algorithm
• The pressure distribution in thermally bistable turbulent flows
• On the structure of molecular clouds
• The Dependence of Star Formation Efficiency on Gas Surface Density
• An Evolutionary Model for Collapsing Molecular Clouds and Their Star Formation Activity. II. Mass Dependence of the Star Formation Rate
• Molecular Line Observations of Infrared Dark Clouds II: Physical Conditions
• Prestellar Core Formation, Evolution, and Accretion from Gravitational Fragmentation in Turbulent Converging Flows
• A Simple Perspective on the Mass-Area Relationship in Molecular Clouds
• Interstellar MHD Turbulence and Star Formation
• Molecular cloud formation as seen in synthetic Hi and molecular gas observations
• Identification of a Fundamental Transition in a Turbulently-Supported Interstellar Medium
• Testing assumptions and predictions of star-formation theories

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• Global Hierarchical Collapse In Molecular Clouds. Towards a Comprehensive Scenario
• Cloud-Scale Molecular Gas Properties in 15 Nearby Galaxies
• The molecular cloud lifecycle
• Molecular Cloud Populations in the Context of Their Host Galaxy Environments: A Multiwavelength Perspective
• A Model for the Onset of Self-gravitation and Star Formation in Molecular Gas Governed by Galactic Forces: I. Cloud-scale Gas Motions
• Testing Larson's relationships in massive clumps
• From diffuse gas to dense molecular cloud cores
• The magnetic field structure in molecular cloud filaments
• WISDOM Project -- IX Giant Molecular Clouds in the Lenticular Galaxy NGC4429: Effects of Shear and Tidal Forces on Clouds
• The effect of photoionising feedback on the shaping of hierarchically-forming stellar clusters
• Structure and Expansion Law of HII Regions in structured Molecular Clouds
• Multi-scale dynamics in star-forming regions: the interplay between gravity and turbulence
• The core and stellar mass functions in massive collapsing filaments
• The Galactic Census of High- and Medium-mass Protostars. IV. Molecular Clump Radiative Transfer, Mass Distributions, Kinematics, and Dynamical Evolution
• Thermal balance and comparison of gas and dust properties of dense clumps in the Hi-GAL survey
• Fragmentation and filaments at the onset of star and cluster formation: SABOCA 350 $\mu$m view of ATLASGAL selected massive clumps
• The evolution of temperature and density structures of OB cluster-forming molecular clumps
• A possible observational bias in the estimation of the virial parameter in virialized clumps
• Non-adiabatic turbulence driving during gravitational collapse
• Simultaneous evolution of the virial parameter and star formation rate in molecular clumps undergoing global hierarchical collapse
• CO(2-1) Survey at 9 parsec resolution in the SMC
• Evolution of the angular momentum during gravitational fragmentation of molecular clouds
• High-resolution APEX/LAsMA ${}^{12}$CO and ${}^{13}$CO (3-2) observation of the G333 giant molecular cloud complex : II. Survival and gravitational collapse of dense gas structures under feedback
• The kinetic and magnetic energy budget of hub-filament systems during the gravitational fragmentation of molecular clouds
• Gravitational instability of filamentary molecular clouds, including ambipolar diffusion; Non-isothermal filament
• A stochastic and analytical model of hierarchical fragmentation: The fragmentation of gas structures into young stellar objects in the interstellar medium
• Unveiling the gravitationally unstable disc of a massive star-forming galaxy using NOEMA and MUSE
• The Hierarchical Dynamical State of Molecular Gas from 3 to 300 pc in NGC 253
• Why most molecular clouds are gravitationally dominated