Simultaneous evolution of the virial parameter and star formation rate in molecular clumps undergoing global hierarchical collapse

Abstract

We compare dense clumps and cores in a numerical simulation of molecular clouds (MCs) undergoing global hierarchical collapse (GHC) to observations in two MCs at different evolutionary stages, the Pipe and the G14.225 clouds, to test the ability of the GHC scenario to follow the early evolution of the energy budget and star formation activity of these structures. In the simulation, we select a region that contains cores of sizes and densities similar to the Pipe cores, and find that it evolves through accretion, developing substructure similar to that of G14.225 cloud after $\sim 1.6$ Myr. Within this region, we follow the evolution of the Larson ratio $\mathcal{L}\equiv {\sigma }_{\mathrm{v}}/R^{1/2}$, where ${\sigma }_{\mathrm{v}}$ is the velocity dispersion and $R$ is the size, the virial parameter $\alpha$, and the star formation activity of the cores/clumps. In the simulation, we find that as the region evolves: $i)$ its clumps have $\mathcal{L}$ and $\alpha$ values first consistent with those of the Pipe substructures and later with those of G14.225; $ii)$ the individual cores first exhibit a decrease in $\alpha$ followed by an increase when star formation begins; $iii)$ collectively, the ensemble of cores/clumps reproduces the observed trend of lower $\alpha$ for higher-mass objects, and $iv)$ the star formation rate and star formation efficiency increase monotonically. We suggest that this evolution is due to the simultaneous loss of externally-driven compressive kinetic energy and increase of the self-gravity-driven motions. We conclude that the GHC scenario provides a realistic description of the evolution of the energy budget of the clouds' substructure at early times, which occurs simultaneously with an evolution of the star formation activity.

arXiv commentAccepted for publication in ApJ

References in corpus (71)

• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The cosmological simulation code GADGET-2
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Theory of Star Formation
• Control of star formation by supersonic turbulence
• On the Star Formation Rates in Molecular Clouds
• Re-examining Larson's Scaling Relationships in Galactic Molecular Clouds
• Structural Analysis of Molecular Clouds: Dendrograms
• The mass function of dense molecular cores and the origin of the IMF
• Outflow Feedback Regulated Massive Star Formation in Parsec-Scale Cluster Forming Clumps
• Global Hierarchical Collapse In Molecular Clouds. Towards a Comprehensive Scenario
• Low Virial Parameters in Molecular Clouds: Implications for High Mass Star Formation and Magnetic Fields
• Gravity or Turbulence? The velocity dispersion-size relation
• The Nature of the Dense Core Population in the Pipe Nebula: Thermal Cores Under Pressure
• Clump morphology and evolution in MHD simulations of molecular cloud formation
• Clouds as Turbulent Density Fluctuations. Implications for pressure confinement and spectral line data interpretation
• 2MASS wide field extinction maps - I. The Pipe nebula
• ALMA Reveals the Molecular Medium Fueling the Nearest Nuclear Starburst
• Supernova Driving. I. The Origin of Molecular Cloud Turbulence
• Physical vs. Observational Properties of Clouds in Turbulent Molecular Cloud Models
• Why are most molecular clouds not gravitationally bound?
• On the evolution of the density pdf in strongly self-gravitating systems
• Observational Evidence of Dynamic Star Formation Rate in Milky Way Giant Molecular Clouds
• Trigonometric Parallaxes of Massive Star Forming Regions: VIII. G12.89+0.49, G15.03-0.68 (M17) and G27.36-0.16
• The Two States of Star Forming Clouds
• High- and Low-Mass Star Forming Regions from Hierarchical Gravitational Fragmentation. High local Star Formation Rates with Low Global Efficiencies
• A Massive Prestellar Clump Hosting no High-Mass Cores
• Hierarchical Cluster Assembly in Globally Collapsing Clouds
• Mutual influence of supernovae and molecular clouds
• A Search for Larson-Type Relations in Numerical Simulations of the ISM. Evidence for Non-Constant Column Densities
• Unveiling a network of parallel filaments in the Infrared Dark Cloud G14.225-0.506
• Filamentary Accretion Flows in the Infrared Dark Cloud G14.225-0.506 Revealed by ALMA
• Gravitational contraction versus Supernova driving and the origin of the velocity dispersion-size relation in molecular clouds
• ALMA resolves the spiraling accretion flow in the luminous OB cluster forming region G33.92+0.11
• Infall Signatures in a Prestellar Core embedded in the High-Mass 70 $\mu$m Dark IRDC G331.372-00.116
• Does External Pressure Explain Recent Results for Molecular Clouds?
• Star Cluster Formation in a Turbulent Molecular Cloud Self-Regulated by Photo-Ionisation Feedback
• The nature of the dense core population in the Pipe Nebula: A survey of NH3, CCS, and HC5N molecular line emission
• Dense core properties in the Infrared Dark cloud G14.225-0.506 revealed by ALMA
• An Evolutionary Model for Collapsing Molecular Clouds and Their Star Formation Activity
• The Spitzer c2d Survey of Nearby Dense Cores: IV. Revealing the Embedded Cluster in B59
• On The Nature of Variations in the Measured Star Formation Efficiency of Molecular Clouds
• rpSPH: a novel Smoothed Particle Hydrodynamics Algorithm
• Properties of dense cores in clustered massive star-forming regions at high angular resolution
• Evidence for Delayed Massive Star Formation in the M17 Proto-OB Association
• Massive 70 micron quiet clumps II: non-thermal motions driven by gravity in massive star formation?
• Hierarchical Structure of Magnetohydrodynamic Turbulence In Position-Position-Velocity Space
• What is controlling the fragmentation process in the Infrared Dark Cloud G14.225-0.506? Differet level of fragmentation in twin hubs
• Gravity or turbulence? IV. Collapsing cores in out-of-virial disguise
• The nature of the dense core population in the pipe nebula: core and cloud kinematics from C18O observations
• An Evolutionary Model for Collapsing Molecular Clouds and Their Star Formation Activity. II. Mass Dependence of the Star Formation Rate
• Young starless cores embedded in the magnetically dominated Pipe Nebula
• Cloud structure of three Galactic infrared dark star-forming regions from combining ground and space based bolometric observations
• Deep Near-Infrared Survey of the Pipe Nebula II: Data, Methods, and Dust Extinction Maps
• Rapid Circumstellar Disk Evolution and an Accelerating Star Formation Rate in the Infrared Dark Cloud M17 SWex
• Energy budget of forming clumps in numerical simulations of collapsing clouds
• The effect of the virial state of molecular clouds on the influence of feedback from massive stars
• Statistics of Core Lifetimes in Numerical Simulations of Turbulent, Magnetically Supercritical Molecular Clouds
• The mid-infrared extinction law in the darkest cores of the Pipe Nebula
• Low-mass protostars and dense cores in different evolutionary stages in IRAS 00213+6530
• Lack of high-mass prestellar cores in the starless MDCs of NGC6334
• Formation of dense structures induced by filament collisions. Correlation of density, kinematics and magnetic field in the Pipe nebula
• A possible observational bias in the estimation of the virial parameter in virialized clumps
• Molecular Cloud Evolution VI. Measuring cloud ages
• The Accelerating Pace of Star Formation
• Molecular cloud formation as seen in synthetic Hi and molecular gas observations
• Evidence and Implications of Pressure Fluctuations in the ISM
• Young starless cores embedded in the magnetically dominated Pipe Nebula. II. Extended dataset
• A survey of molecular cores in M17 SWex
• Gravity as the main driver of non-thermal motions in massive star formation

Cited by in corpus (10)

• Planet formation via pebble accretion in externally photoevaporating discs
• The evolution of temperature and density structures of OB cluster-forming molecular clumps
• Evolution of the angular momentum during gravitational fragmentation of molecular clouds
• Hyperfine Group Ratio: A Recipe for Deriving Kinetic Temperature from Ammonia Inversion Lines
• The kinetic and magnetic energy budget of hub-filament systems during the gravitational fragmentation of molecular clouds
• Interstellar Nitrogen Isotope Ratios: New NH3 Data from the Galactic Center out to the Perseus Arm
• Physical Properties and Kinematics of Dense Cores Associated with Regions of Massive Star Formation from the Southern Sky
• Gravity or turbulence? VII. The Schmidt-Kennicutt law, the star formation efficiency, and the mass density of clusters from gravitational collapse rather than turbulent support
• Star Cluster Formation in Clouds with Externally Driven Turbulence
• The Hierarchical Dynamical State of Molecular Gas from 3 to 300 pc in NGC 253