Massive 70 micron quiet clumps II: non-thermal motions driven by gravity in massive star formation?

Abstract

The dynamic activity in massive star forming regions prior to the formation of bright protostars is still not fully investigated. In this work we present observations of HCO+ J=1-0 and N2H+ J=1-0 made with the IRAM 30m telescope towards a sample of 16 Herschel-identified massive 70 micron quiet clumps associated with infrared dark clouds. The clumps span a mass range from 300 M_sun to 2000 M_sun. The N2H+ data show that the regions have significant non-thermal motions with velocity dispersion between 0.28 km s^-1 and 1.5 km s^-1, corresponding to Mach numbers between 2.6 and 11.5. The majority of the 70 micron quiet clumps have asymmetric HCO+ line profiles, indicative of significant dynamical activity. We show that there is a correlation between the degree of line asymmetry and the surface density Sigma of the clumps, with clumps of Sigma>=0.1 g cm^-2 having more asymmetric line profiles, and so are more dynamically active, than clumps with lower Sigma. We explore the relationship between velocity dispersion, radius and Sigma and show how it can be interpreted as a relationship between an acceleration generated by the gravitational field a_G, and the measured kinetic acceleration, a_k, consistent with the majority of the non-thermal motions originating from self-gravity. Finally, we consider the role of external pressure and magnetic fields in the interplay of forces.

arXiv commentAccepted for publication in MNRAS. 12 pages, 10 figures. arXiv admin note: substantial text overlap with arXiv:1511.03670

References in corpus (30)

• Theory of Star Formation
• The Stellar IMF from Turbulent Fragmentation
• The Formation of Massive Stars from Turbulent Cores
• ATLASGAL - The APEX Telescope Large Area Survey of the Galaxy at 870 microns
• Re-examining Larson's Scaling Relationships in Galactic Molecular Clouds
• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• Slow Star Formation in Dense Gas: Evidence and Implications
• The Universality of Turbulence in Galactic Molecular Clouds
• Low Virial Parameters in Molecular Clouds: Implications for High Mass Star Formation and Magnetic Fields
• The Bolocam Galactic Plane Survey: Survey Description and Data Reduction
• Gravity or Turbulence? The velocity dispersion-size relation
• ATLASGAL --- towards a complete sample of massive star forming clumps
• A Comparative Study of Giant Molecular Clouds in M51, M33 and the Large Magellanic Cloud
• Why are most molecular clouds not gravitationally bound?
• The Dynamics of Massive Starless Cores with ALMA
• Probing the formation of intermediate- to high-mass stars in protoclusters: A detailed millimeter study of the NGC 2264 clumps
• Probing the initial conditions of high-mass star formation. II. Fragmentation, stability, and chemistry
• High- and Low-Mass Star Forming Regions from Hierarchical Gravitational Fragmentation. High local Star Formation Rates with Low Global Efficiencies
• Gravity or turbulence? -III. Evidence of pure thermal Jeans fragmentation at ~0.1 pc scale
• Chemistry in Infrared Dark Clouds
• Mapping the column density and dust temperature structure of IRDCs with Herschel
• Gravitational contraction versus Supernova driving and the origin of the velocity dispersion-size relation in molecular clouds
• What can simulated molecular clouds tell us about real molecular clouds?
• Properties of dense cores in clustered massive star-forming regions at high angular resolution
• Sub-Alfvenic Non-Ideal MHD Turbulence Simulations with Ambipolar Diffusion: II. Comparison with Observation, Clump Properties, and Scaling to Physical Units
• Line Profiles of Cores within Clusters: II Signatures of Dynamical Collapse during High Mass Star Formation
• The end of star formation in Chamaeleon I ? A LABOCA census of starless and protostellar cores
• Molecular Line Observations of Infrared Dark Clouds II: Physical Conditions
• Massive 70 micron quiet clumps I: evidence of embedded low/intermediate-mass star formation activity
• Line Profiles of Cores within Clusters. III. What is the most reliable tracer of core collapse in dense clusters?

Cited by in corpus (37)

• Star Clusters Across Cosmic Time
• Global Hierarchical Collapse In Molecular Clouds. Towards a Comprehensive Scenario
• Gravity drives the evolution of infrared dark hubs: JVLA observations of SDC13
• Disruption of giant molecular clouds and formation of bound star clusters under the influence of momentum stellar feedback
• Testing Larson's relationships in massive clumps
• From diffuse gas to dense molecular cloud cores
• The SEDIGISM survey: Molecular clouds in the inner Galaxy
• Feedback from OB stars on their parent cloud: Gas exhaustion rather than gas ejection
• Massive Star Formation via the Collapse of Subvirial and Virialized Turbulent Massive Cores
• The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). VIII. Dynamics of Embedded Dense Cores
• HII regions and high-mass starless clump candidates II. Fragmentation and induced star formation at ~0.025 pc scale: An ALMA continuum study
• Multi-scale dynamics in star-forming regions: the interplay between gravity and turbulence
• The SQUALO project (Star formation in QUiescent And Luminous Objects) I: clump-fed accretion mechanism in high-mass star-forming objects
• Asymmetric Line Profiles in Dense Molecular Clumps Observed in MALT90: Evidence for Global Collapse
• Turbulence in a self-gravitating molecular cloud core
• Multi-scale analysis of the Monoceros OB 1 star-forming region: II. Colliding filaments in the Monoceros OB1 molecular cloud
• The Forgotten Quadrant Survey. ${}^{12}$CO and ${}^{13}$CO (1-0) survey of the Galactic Plane in the range 220°$<l<$240° -2.5°$<b<$0°
• Are massive dense clumps truly sub-virial? A new analysis using Gould Belt ammonia data
• A possible observational bias in the estimation of the virial parameter in virialized clumps
• Non-adiabatic turbulence driving during gravitational collapse
• Molecular cloud catalogue from ${}^{13}$CO(1-0) data of the Forgotten Quadrant Survey
• Simultaneous evolution of the virial parameter and star formation rate in molecular clumps undergoing global hierarchical collapse
• Unveiling the formation of the massive DR21 ridge
• The Evolutionary Status of Protostellar Clumps Hosting Class II Methanol Masers
• The Cloud Factory II: Gravoturbulent Kinematics of Resolved Molecular Clouds in a Galactic Potential
• Formation of hub-filament structure triggered by cloud-cloud collision in W33 complex
• The TOP-SCOPE survey of PGCCs: PMO and SCUBA-2 observations of 64 PGCCs in the 2nd Galactic Quadrant
• Searching for Inflow Towards Massive Starless Clump Candidates Identified in the Bolocam Galactic Plane Survey
• YSO jets in the Galactic Plane from UWISH2: V - Jets and Outflows in M17
• APEX CO observations towards the photodissociation region of RCW120
• 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
• A survey of SiO $J=$ 1 -- 0 emission toward massive star-forming regions
• High-Mass Starless Clumps: Dynamical State and Correlation Between Physical Parameters
• The kinetic and magnetic energy budget of hub-filament systems during the gravitational fragmentation of molecular clouds
• Virial Ratio: Direct Evaluation from Molecular Cloud Data and the Challenges of Improving Accuracy
• The Planck submillimeter properties of Galactic high-mass star forming regions: dust temperatures, luminosities, masses and Star Formation Efficiency