W51North: A protocluster emerging out of a thermally inhibited fragmenting cloud
arXiv:2109.07658 · doi:10.1051/0004-6361/202038741
Abstract
The fragmentation process in massive star-forming regions is one of the contemporary problems in astrophysics, and several physical processes have been proposed to control the fragmentation including turbulence, magnetic field, rotation, stellar feedback, and gravity. However, the fragmentation process has been poorly studied at small spatial scales well below 1000 AU. We aim to use ALMA (Atacama Large Millimeter and Submillimeter Array) high angular resolution data to identify the fragments in W51 IRS2 and to study the fragmentation properties on a spatial scale of 200 AU. We used ALMA data of W51 IRS2 from three projects, which give an angular resolution of 0.028 (144 AU) at millimeter wavelengths. We identified compact fragments by using {\it uv}-range constrained 1.3 mm continuum data. A Mean Surface Density of Companions (MSDC) analysis has been performed to study the separations between fragments. A total number of 33 continuum sources are identified and 29 out of them are defined as fragments in the surveyed region.The MSDC analysis reveals two breaks corresponding to spatial sales of 1845 AU and 7346 AU, indicative of a two-level clustering phenomenon, along with a linear regime below 1845 AU, mostly associated with W51 North, whose slope is consistent with the slope for the clustering regime of other cluster-like regions in the Galaxy. The typical masses and separations of the fragments as well as the relation between density and number of fragments can be explained through a thermal Jeans process operating at high temperatures of 200--400 K, consistent with previous measurements of the temperature in the region, and produced by the nearby massive stars. Therefore, although W51 IRS2 seems to be undergoing a thermally inhibited fragmentation phase, this does not seem to prevent the formation of a protocluster associated with W51 North.
References in corpus (46)
- Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
- Cores, filaments, and bundles: hierarchical core formation in the L1495/B213 Taurus region
- Radiation-Hydrodynamic Simulations of Collapse and Fragmentation in Massive Protostellar Cores
- Global Hierarchical Collapse In Molecular Clouds. Towards a Comprehensive Scenario
- On the Role of Disks in the Formation of Stellar Systems: A Numerical Parameter Study of Rapid Accretion
- Hierarchical fragmentation and differential star formation in the Galactic "Snake": infrared dark cloud G11.11-0.12
- A Correlation Between Surface Densities of Young Stellar Objects and Gas in Eight Nearby Molecular Clouds
- Collapse of massive magnetized dense cores using radiation-magneto-hydrodynamics: early fragmentation inhibition
- The ALMA Survey of 70 m dark High-mass clumps in Early Stages (ASHES). I. Pilot Survey: Clump Fragmentation
- Limiting Accretion onto Massive Stars by Fragmentation-Induced Starvation
- Collapse, outflows and fragmentation of massive, turbulent and magnetized prestellar barotropic cores
- The Fragmentation of Magnetized, Massive Star-Forming Cores with Radiative Feedback
- Chains of dense cores in the Taurus L1495/B213 complex
- Probing the initial conditions of high-mass star formation. II. Fragmentation, stability, and chemistry
- Hierarchical Fragmentation and Jet-like Outflows in IRDC G28.34+0.06, a Growing Massive Protostar Cluster
- Gravity or turbulence? -III. Evidence of pure thermal Jeans fragmentation at ~0.1 pc scale
- Identifying Primordial Substructure in NGC 2264
- Spatial Distributions of Young Stars
- Interpreting the Mean Surface Density of Companions in Star-Forming Regions
- Hierarchical Fragmentation of the Orion Molecular Filaments
- Centrally condensed turbulent cores: Massive stars or fragmentation?
- Star Formation Efficiency in Driven, Supercritical, Turbulent Clouds
- Thermal Feedback in the high-mass star and cluster forming region W51
- Multi-directional mass-accretion and collimated outflows in W51
- Forming an Early O-type Star Through Gas Accretion?
- Toward gas exhaustion in the W51 high-mass protoclusters
- Star-forming content of the giant molecular filaments in the Milky Way
- Stellar mass spectrum within massive collapsing clumps II. Thermodynamics and tidal forces of the first Larson core
- A Survey of the Mon R2 Giant Molecular Cloud: Analysis of the Gas Column Density Probability Density Function
- Physical and radiative properties of the first core accretion shock
- The JCMT Gould Belt Survey: A First Look at Southern Orion A with SCUBA-2
- Mass Assembly of Stellar Systems and Their Evolution with the SMA (MASSES). Multiplicity and the Physical Environment in L1448N
- Outflow 20--2000 AU from a High-Mass Protostar in W51-IRS2
- Three intermediate-mass YSOs with different properties emerging from the same natal cloud in IRAS 00117+6412
- Magnetically-regulated fragmentation of a massive, dense and turbulent clump
- HII regions and high-mass starless clump candidates II. Fragmentation and induced star formation at ~0.025 pc scale: An ALMA continuum study
- Extremely large and hot multilayer Keplerian disk around the O-type protostar W51N: The precursors of the HCHII regions?
- Fitting density models to observational data - The local Schmidt law in molecular clouds
- Early science with the Large Millimetre Telescope: An LMT/AzTEC 1.1 mm Survey of Dense Cores in the Monoceros R2 Giant Molecular Cloud
- The role of the magnetic field in the fragmentation process: the case of G14.225-0.506
- APEX/SABOCA observations of small-scale structure of infrared-dark clouds I. Early evolutionary stages of star-forming cores
- How first hydrostatic cores, tidal forces and gravo-turbulent fluctuations set the characteristic mass of stars
- A dense micro-cluster of Class 0 protostars in NGC 2264 D-MM1
- Primordial Mass and Density Segregation in a Young Molecular Cloud
- Not so different after all: Properties and Spatial Structure of Column Density Peaks in the Pipe and Orion A Clouds
- The mean surface density of companions in a stellar-dynamical context