The Structure, Dynamics and Star Formation Rate of the Orion Nebula Cluster

Abstract

The spatial morphology and dynamical status of a young, still-forming stellar cluster provide valuable clues on the conditions during the star formation event and the processes that regulated it. We analyze the Orion Nebula Cluster (ONC), utilizing the latest censuses of its stellar content and membership estimates over a large wavelength range. We determine the center of mass of the ONC, and study the radial dependence of angular substructure. The core appears rounder and smoother than the outskirts, consistent with a higher degree of dynamical processing. At larger distances the departure from circular symmetry is mostly driven by the elongation of the system, with very little additional substructure, indicating a somewhat evolved spatial morphology or an expanding halo. We determine the mass density profile of the cluster, which is well fitted by a power law that is slightly steeper than a singular isothermal sphere. Together with the ISM density, estimated from average stellar extinction, the mass content of the ONC is insufficient by a factor $\sim 1.8$ to reproduce the observed velocity dispersion from virialized motions, in agreement with previous assessments that the ONC is moderately supervirial. This may indicate recent gas dispersal. Based on the latest estimates for the age spread in the system and our density profiles, we find that, at the half-mass radius, 90% of the stellar population formed within $\sim 5$-$8$ free-fall times ($t_{\mathrm{ff}}$). This implies a star formation efficiency per $t_{\mathrm{ff}}$ of ${\epsilon }_{\mathrm{ff}}\sim 0.04$-$0.07$, i.e., relatively slow and inefficient star formation rates during star cluster formation.

arXiv commentApJ accepted; 17 pages, 13 figures

References in corpus (54)

• On the variation of the Initial Mass Function
• Embedded Clusters in Molecular Clouds
• A General Theory of Turbulence-Regulated Star Formation, From Spirals to ULIRGs
• The distance to the Orion Nebula
• A Spitzer Survey of Young Stellar Clusters within One Kiloparsec of the Sun: Cluster Core Extraction and Basic Structural Analysis
• Slow Star Formation in Dense Gas: Evidence and Implications
• Rapid Formation of Molecular Clouds and Stars in the Solar Neighborhood
• Star Formation in a Crossing Time
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• The Star Formation Rate of Supersonic MHD Turbulence
• The Spitzer Space Telescope Survey of the Orion A & B Molecular Clouds - Part I: A Census of Dusty Young Stellar Objects and a Study of their Mid-IR Variability
• An ACS Survey of Globular Clusters V: Star Catalog for Each Cluster
• Chandra Orion Ultradeep Project: Observations and Source Lists
• On the origin of the O and B-type stars with high velocities II Runaway stars and pulsars ejected from the nearby young stellar groups
• The statistical Analysis of Star Clusters
• Dynamical mass segregation on a very short timescale
• Determination of the gas-to-dust ratio in nearby dense clouds using X-ray absorption measurements
• Protostellar Turbulence Driven by Collimated Outflows
• Episodic accretion at early stages of evolution of low mass stars and brown dwarfs: a solution for the observed luminosity spread in HR diagrams?
• Global X-ray properties of the Orion Nebula region
• Equilibrium Star Cluster Formation
• On the Rapid Collapse and Evolution of Molecular Clouds
• The Initial Configuration of Young Stellar Clusters: A K-band Number Counts Analysis of the Surface Density of Stars
• A Multi-color Optical Survey of the Orion Nebula Cluster. II. the H-R diagram
• The early dynamical evolution of cool, clumpy star clusters
• Dynamical evolution of star forming regions
• On the Structure of the Orion A Cloud and the Formation of the Orion Nebula Cluster
• The Spatial Structure of Young Stellar Clusters. I. Subclusters
• Kinematics of the Orion Nebula Cluster: Velocity Substructure and Spectroscopic Binaries
• The Initial Mass Function of the Orion Nebula Cluster across the H-burning limit
• Observed luminosity spread in young clusters and Fu Ori stars: a unified picture
• Membership of the Orion Nebula Population from the Chandra Orion Ultradeep Project
• Dynamics of Dense Cores in the Perseus Molecular Cloud
• On the Reliability of Stellar Ages and Age Spreads Inferred from Pre-Main Sequence Evolutionary Models
• Kinematic Structure of the Orion Nebula Cluster and its Surroundings
• Quantitative Evidence for an Intrinsic Age Spread in the Orion Nebula Cluster
• No wide spread of stellar ages in the Orion Nebula Cluster
• Spiral shocks, triggering of star formation and the velocity dispersion in Giant Molecular Clouds
• Rapid Star Formation and Global Gravitational Collapse
• Characterizing the dynamical state of star clusters from snapshots of their spatial distributions
• The Becklin-Neugebauer Object as a Runaway B Star, Ejected 4000 years ago from the theta^1C system
• Dynamical Evolution of Young Embedded Clusters: A Parameter Space Survey
• An Enhanced Spectroscopic Census of the Orion Nebula Cluster
• Core-Halo Age Gradients and Star Formation in the Orion Nebula and NGC~2024 Young Stellar Clusters
• A New Method for the Assessment of Age and Age-Spread of Pre-Main Sequence Stars in Young Stellar Associations of the Magellanic Clouds
• 2MASS wide field extinction maps: IV. The Orion, Mon R2, Rosette, and Canis Major star forming regions
• A Wide-Field Survey of the Orion Nebula Cluster in the Near-Infrared
• Confronting Outflow-Regulated Cluster Formation Model with Observations
• Merging time-scales of stellar sub-clumps in young star-forming regions
• The role of low-mass star clusters in massive star formation. The Orion Case
• Gravitational Slingshot of Young Massive Stars in Orion
• The extinction map of the OMC-1 molecular cloud behind the Orion Nebula
• The multiplicity of massive stars in the Orion Nebula cluster as seen with long-baseline interferometry
• Strong Biases in Estimating the Time Dependence of Mass Accretion Rates in Young Stars

Cited by in corpus (60)

• Star Clusters Across Cosmic Time
• Kinematics in Young Star Clusters and Associations with Gaia DR2
• Modeling UV Radiation Feedback from Massive Stars: II. Dispersal of Star-Forming Giant Molecular Clouds by Photoionization and Radiation Pressure
• IN-SYNC IV - The Young Stellar Population in the Orion A Molecular Cloud
• Structure, kinematics, and ages of the young stellar populations in the Orion region
• Disruption of Molecular Clouds by Expansion of Dusty H II Regions
• Expanding bubbles in Orion A: [CII] observations of M42, M43, and NGC 1977
• Star Cluster Formation in a Turbulent Molecular Cloud Self-Regulated by Photo-Ionisation Feedback
• GMC Collisions as Triggers of Star Formation. III. Density and Magnetically Regulated Star Formation
• Unbound Young Stellar Systems: Star Formation on the loose
• GMC Collisions as Triggers of Star Formation. II. 3D Turbulent, Magnetized Simulations
• How do bound star clusters form?
• IN-SYNC. V. Stellar kinematics and dynamics in the Orion A Molecular Cloud
• A solution to the proplyd lifetime problem
• Slingshot Mechanism for Clusters: Gas Density Regulates Star Density in the Orion Nebula Cluster (M42)
• Signatures of star cluster formation by cold collapse
• GMC Collisions as Triggers of Star Formation. I. Parameter Space Exploration with 2D Simulations
• Dynamical evolution of fractal structures in star-forming regions
• Stellar Proper Motions in the Orion Nebula Cluster
• The Gaia-ESO Survey: Structural and dynamical properties of the young cluster Chamaeleon I
• Numerical Simulations of Turbulent Molecular Clouds Regulated by Radiation Feedback Forces II: Radiation-Gas Interactions and Outflows
• The APOGEE-2 Survey of the Orion Star Forming Complex: I. Target Selection and Validation with early observations
• The Distribution of Mass Surface Densities in a High-Mass Protocluster
• The VMC Survey. XXIX. Turbulence-Controlled Hierarchical Star Formation in the Small Magellanic Cloud
• The 3-D Kinematics of the Orion Nebula Cluster: NIRSPEC-AO Radial Velocities of the Core Population
• Hunting for Runaways from the Orion Nebula Cluster
• Mapping young stellar populations towards Orion with Gaia DR1
• The Structural Evolution of Forming and Early Stage Star Clusters
• Winds in Star Clusters Drive Kolmogorov Turbulence
• Molecular Cloud Evolution VI. Measuring cloud ages
• The GALAH survey: Chemical homogeneity of the Orion complex
• HST survey of the Orion Nebula Cluster in the H${}_2$O 1.4 $\mu$m absorption band: II. The substellar IMF down to planetary masses
• Star Cluster Formation from Turbulent Clumps. II. Gradual Star Cluster Formation
• Low Mass Stars as Tracers of Star and Cluster Formation
• Kiloparsec-Scale Simulations of Star Formation in Disk Galaxies. IV. Regulation of Galactic Star Formation Rates by Stellar Feedback
• GMC Collisions as Triggers of Star Formation. VII. The Effect of Magnetic Field Strength on Star Formation
• [CII] $158\mu \mathrm{m}$ line emission from Orion A. I. A template for extragalactic studies?
• The Dynamics, Structure, and Fate of a Young Cluster During Gas Dispersal: Hectoschelle, Chandra, Spitzer, and Gaia Observations of CepOB3b
• A gravitational and dynamical framework of star formation: The Orion Nebula
• Binary Formation in the Orion Nebula Cluster: Exploring the Sub-stellar Limit
• HST astrometry in the Orion Nebula Cluster: census of low-mass runaways
• Testing Feedback from Star Clusters in Simulations of the Milky Way Formation
• Astrochemical modelling of infrared dark clouds
• SIRIUS Project. IV. The formation history of the Orion Nebula Cluster driven by clump mergers
• Magnetic Fields and Galactic Star Formation Rates
• Quantifying kinematic substructure in star-forming regions with statistical tests of spatial autocorrelation
• Expansion Kinematics of Young Clusters. I. Lambda Ori
• Core Emergence in a Massive Infrared Dark Cloud: A Comparison Between Mid-IR Extinction and 1.3 mm Emission
• Simulated observations of star formation regions: infrared evolution of globally collapsing clouds
• Which young clusters/associations are we missing today?
• The 3D Kinematics of the Orion Nebula Cluster II: Mass-dependent Kinematics of the Inner Cluster
• Report on Optimal Substructure Techniques for Stellar, Gas and Combined Samples
• Analysis of Selected Runaway Stars in the Orion Nebula Based on Data from the Gaia EDR3 Catalogue
• Theory of Turbulent Equilibrium Spheres with Power-Law Linewidth-Size Relation
• Water emission tracing active star formation from the Milky Way to high-$z$ galaxies
• An X-ray View of Two Infrared Dark Clouds G034.43+00.24 and G035.39-00.33
• Stirred, not shaken: Star cluster survival in the slingshot scenario
• Comparison of Low-Mass and High-Mass Star Formation
• Fire from Ice - Massive Star Birth from Infrared Dark Clouds
• From Interstellar Clouds to Stars