ALMA Observations of Massive Clouds in the Central Molecular Zone: Jeans Fragmentation and Cluster Formation

Abstract

We report ALMA Band 6 continuum observations of 2000 AU resolution toward four massive molecular clouds in the Central Molecular Zone of the Galaxy. To study gas fragmentation, we use the dendrogram method to identify cores as traced by the dust continuum emission. The four clouds exhibit different fragmentation states at the observed resolution despite having similar masses at the cloud scale ($\sim$1--5 pc). Assuming a constant dust temperature of 20 K, we construct core mass functions of the clouds and find a slightly top-heavy shape as compared to the canonical initial mass function, but we note several significant uncertainties that may affect this result. The characteristic spatial separation between the cores as identified by the minimum spanning tree method, $\sim$$10^4$ AU, and the characteristic core mass, 1--7 $M_{\odot }$, are consistent with predictions of thermal Jeans fragmentation. The three clouds showing fragmentation may be forming OB associations (stellar mass $\sim$$10^3$ $M_{\odot }$). None of the four clouds under investigation seem to be currently able to form massive star clusters like the Arches and the Quintuplet ($\sim$$10^4$ $M_{\odot }$), but they may form such clusters by further gas accretion onto the cores.

arXiv commentApJ Letters accepted. Slightly updated to match the published version. A full catalog of the identified cores is available as a machine-readable table on the publisher website or on Zenodo (https://doi.org/10.5281/zenodo.3735708)

References in corpus (44)

• Power-law distributions in empirical data
• On the variation of the Initial Mass Function
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty
• Analytical theory for the initial mass function: CO clumps and prestellar cores
• Structural Analysis of Molecular Clouds: Dendrograms
• HST/NICMOS Observations of Massive Stellar Clusters Near the Galactic Center
• Variations in the Galactic star formation rate and density thresholds for star formation
• The lifecycle of molecular clouds in nearby star-forming disc galaxies
• What controls star formation in the central 500 pc of the Galaxy?
• Hierarchical fragmentation and differential star formation in the Galactic "Snake": infrared dark cloud G11.11-0.12
• Fast and inefficient star formation due to short-lived molecular clouds and rapid feedback
• The dynamical evolution of molecular clouds near the Galactic Centre - I. Orbital structure and evolutionary timeline
• Fragmentation at the Earliest Phase of Massive Star Formation
• The ALMA Survey of 70 $\mu$m dark High-mass clumps in Early Stages (ASHES). I. Pilot Survey: Clump Fragmentation
• The link between turbulence, magnetic fields, filaments, and star formation in the Central Molecular Zone cloud G0.253+0.016
• Star formation rates and efficiencies in the Galactic Centre
• The earliest phases of star formation - A Herschel key project. The thermal structure of low-mass molecular cloud cores
• The unexpectedly large proportion of high-mass star-forming cores in a Galactic mini-starburst
• The Galactic Center Molecular Cloud Survey. I. A Steep Linewidth-Size Relation & Suppression of Star Formation
• The Dawes Review 8: Measuring the Stellar Initial Mass Function
• Turbulence sets the initial conditions for star formation in high-pressure environments
• Distributed star formation throughout the Galactic Center cloud Sgr B2
• The dynamical evolution of molecular clouds near the Galactic Centre - II. Spatial structure and kinematics of simulated clouds
• Infall Signatures in a Prestellar Core embedded in the High-Mass 70 $\mu$m Dark IRDC G331.372-00.116
• Is protostellar heating sufficient to halt fragmentation? A case study of the massive protocluster G8.68-0.37
• Detection of Widespread Hot Ammonia in the Galactic Center
• Seeding the Galactic Centre gas stream: gravitational instabilities set the initial conditions for the formation of protocluster clouds
• A multi-wavelength view of the Galactic center dust ridge reveals little star formation
• The Core Mass Function Across Galactic Environments. II. Infrared Dark Cloud Clumps
• The Core Mass Function in the Massive Protocluster G286.21+0.17 revealed by ALMA
• Star Formation Rates of Massive Molecular Clouds in the Central Molecular Zone
• Star formation in a high-pressure environment: An SMA view of the Galactic centre dust ridge
• The Galactic Center Molecular Cloud Survey. II. A Lack of Dense Gas & Cloud Evolution along Galactic Center Orbits
• A Census of Early Phase High-Mass Star Formation in the Central Molecular Zone
• Comparing Young Massive Clusters and their Progenitor Clouds in the Milky Way
• Thermal Jeans fragmentation within 1000 AU in OMC-1S
• The Molecular Gas Environment in the 20 km s${}^{-1}$ Cloud in the Central Molecular Zone
• Young massive star cluster formation in the Galactic Centre is driven by global gravitational collapse of high-mass molecular clouds
• Physical Properties of the star-forming clusters in NGC 6334
• The orbital motion of the Quintuplet cluster - a common origin for the Arches and Quintuplet clusters?
• Investigating fragmentation of gas structures in OB cluster-forming molecular clump G33.92+0.11 with 1000 AU resolution observations of ALMA
• Properties of the Compact HII Region Complex G-0.02-0.07
• Determining the presence of characteristic fragmentation length-scales in filaments

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• ALMA-IMF I -- Investigating the origin of stellar masses: Introduction to the Large Program and first results
• ALMA-IMF. V. Prestellar and protostellar core populations in the W43 cloud complex
• ALMA-IMF VI -- Investigating the origin of stellar masses: Core mass function evolution in the W43-MM2&MM3 mini-starburst
• ALMA-IMF II -- investigating the origin of stellar masses: Continuum Images and Data Processing
• Star formation in 'the Brick': ALMA reveals an active proto-cluster in the Galactic centre cloud G0.253+0.016
• ALMA Observations of Massive Clouds in the Central Molecular Zone: Ubiquitous Protostellar Outflows
• The centres of M83 and the Milky Way: opposite extremes of a common star formation cycle
• ALMA-IMF. VII. First release of the full spectral line cubes: Core kinematics traced by DCN J=(3-2)
• ALMA observations of the Extended Green Object G19.01$-$0.03: I. A Keplerian disc in a massive protostellar system
• The Core Mass Function Across Galactic Environments. III. Massive Protoclusters
• Virial Clumps in Central Molecular Zone Clouds
• The ALMA-ATOMS survey: Vibrationally excited HC${}_3$N lines in hot cores
• Gravitationally Bound Gas Determines Star Formation in the Galaxy
• The initial conditions for young massive cluster formation in the Galactic Centre: convergence of large-scale gas flows
• Dual-band Unified Exploration of Three CMZ Clouds (DUET). Cloud-wide census of continuum sources showing low spectral indices
• The JWST-NIRCam View of Sagittarius C. II. Evidence for Magnetically Dominated HII Regions in the CMZ
• ALMA observations of massive clouds in the central molecular zone: slim filaments tracing parsec-scale shocks
• ArTéMiS imaging of the filamentary infrared dark clouds G1.75-0.08 and G11.36+0.80: Dust-based physical properties of the clouds and their clumps
• AT 2021hdr: A candidate tidal disruption of a gas cloud by a binary super massive black hole system
• A Core Mass Function Indistinguishable from the Salpeter Stellar Initial Mass Function Using 1000 au Resolution ALMA Observations
• Core mass function of a single giant molecular cloud complex with ~10^4 cores
• Mass Segregation in the CMZoom Survey