Mother of Dragons: A Massive, quiescent core in the dragon cloud (IRDC G028.37+00.07)

Abstract

Context: Core accretion models of massive star formation require the existence of massive, starless cores within molecular clouds. Yet, only a small number of candidates for such truly massive, monolithic cores are currently known. Aims: Here we analyse a massive core in the well-studied infrared-dark cloud (IRDC) called the 'dragon cloud' (also known as G028.37+00.07 or 'Cloud C'). This core (C2c1) sits at the end of a chain of a roughly equally spaced actively star-forming cores near the centre of the IRDC. Methods: We present new high-angular resolution 1 mm ALMA dust continuum and molecular line observations of the massive core. Results: The high-angular resolution observations show that this region fragments into two cores C2c1a and C2c1b, which retain significant background-subtracted masses of 23 Msun and 2 Msun (31 Msun and 6 Msun without background subtraction), respectively. The cores do not appear to fragment further on the scales of our highest angular resolution images (0.200 arcsec, 0.005 pc ~ 1000 AU). We find that these cores are very dense (nH2 > 10^6 cm-3) and have only trans-sonic non-thermal motions (Ms ~ 1). Together the mass, density and internal motions imply a virial parameter of < 1, which suggests the cores are gravitationally unstable, unless supported by strong magnetic fields with strengths of ~ 1 - 10 mG. From CO line observations, we find that there is tentative evidence for a weak molecular outflow towards the lower-mass core, and yet the more massive core remains devoid of any star formation indicators. Conclusions: We present evidence for the existence of a massive, pre-stellar core, which has implications for theories of massive star formation. This source warrants follow-up higher-angular-resolution observations to further assess its monolithic and pre-stellar nature.

arXiv comment8+4 pages, 4+2 Figures, 2 Tables, accepted for publication in Astronomy & Astrophysics

References in corpus (52)

• The Formation of Massive Stars from Turbulent Cores
• Hi-GAL: the Herschel infrared Galactic Plane Survey
• Competitive accretion in embedded stellar cluster
• Structural Analysis of Molecular Clouds: Dendrograms
• Filamentary structure of star-forming complexes
• Realistic Ionizing Fluxes for Young Stellar Populations from 0.05 to twice solar metallicity
• Outflow Feedback Regulated Massive Star Formation in Parsec-Scale Cluster Forming Clumps
• Hierarchical fragmentation and differential star formation in the Galactic "Snake": infrared dark cloud G11.11-0.12
• Magnetic Fields in High-Mass Infrared Dark Clouds
• Fragmentation at the Earliest Phase of Massive Star Formation
• Fragmentation and mass segregation in the massive dense cores of Cygnus X
• Fragmentation of Molecular Clumps and Formation of Protocluster
• The Origin of Massive Stars: The Inertial-Inflow Model
• The Dynamics of Massive Starless Cores with ALMA
• Probing the initial conditions of high-mass star formation. II. Fragmentation, stability, and chemistry
• High-dynamic-range extinction mapping of infrared dark clouds: Dependence of density variance with sonic Mach number in molecular clouds
• Hierarchical Fragmentation and Jet-like Outflows in IRDC G28.34+0.06, a Growing Massive Protostar Cluster
• Gravitational Collapse and Star Formation in Logotropic and Non-Isothermal Spheres
• The dynamical properties of dense filaments in the infrared dark cloud G035.39-00.33
• Mid-Infrared Extinction Mapping of Infrared Dark Clouds: Probing the Initial Conditions for Massive Stars and Star Clusters
• A Massive Prestellar Clump Hosting no High-Mass Cores
• CO outflows from high-mass Class 0 protostars in Cygnus-X
• Gravity or turbulence? -III. Evidence of pure thermal Jeans fragmentation at ~0.1 pc scale
• The Herschel view of massive star formation in G035.39--00.33: Dense and cold filament of W48 undergoing a mini-starburst
• The Galactic Center Cloud G0.253+0.016: A Massive Dense Cloud with low Star Formation Potential
• pyspeckit: A spectroscopic analysis and plotting package
• Complex, Quiescent Kinematics in a Highly Filamentary Infrared Dark Cloud
• NH3 Observations of the Infrared Dark Cloud G28.34+0.06
• An Ordered Bipolar Outflow from a Massive Early-Stage Core
• Gravity, Magnetic Field, and Turbulence: Relative Importance and Impact on Fragmentation in the Infrared Dark Cloud G34.43+00.24
• Investigating the structure and fragmentation of a highly filamentary IRDC
• Protostellar Outflow Heating in a Growing Massive Protocluster
• Unveiling the Early-Stage Anatomy of a Protocluster Hub with ALMA
• Gas Kinematics and Excitation in the Filamentary IRDC G035.39-00.33
• The HI/OH/Recombination line survey of the inner Milky Way (THOR): data release 2 and HI overview
• The Deuterium Fraction in Massive Starless Cores and Dynamical Implications
• The Core Mass Function Across Galactic Environments. II. Infrared Dark Cloud Clumps
• A Hunt for Massive Starless Cores
• Magnetic fields in the infrared dark cloud G34.43+0.24
• G11.92-0.61-MM2: A Bonafide Massive Prestellar Core?
• Magnetic fields in star formation: a complete compilation of all the DCF estimations
• Widespread Molecular Outflows in the Infrared Dark Cloud G28.37+0.07: Indications of Orthogonal Outflow-Filament Alignment
• Detection of a high-mass prestellar core candidate in W43-MM1
• Magnetic fields in the early stages of massive star formation as revealed by ALMA
• ALMA-IRDC: Dense gas mass distribution from cloud to core scales
• CN Zeeman and dust polarization in a high-mass cold clump
• Widespread deuteration across the IRDC G035.39-00.33
• Zooming in to Massive Star Birth
• Lack of high-mass prestellar cores in the starless MDCs of NGC6334
• Similar complex kinematics within two massive, filamentary infrared dark clouds
• SiO Outflows as Tracers of Massive Star Formation in Infrared Dark Clouds
• ALMA-IRDC II. First high-angular resolution measurements of the 14N/15N ratio in a large sample of infrared-dark cloud cores

Cited by in corpus (7)

• ALMA-IMF. VII. First release of the full spectral line cubes: Core kinematics traced by DCN J=(3-2)
• ALMA-IMF XVII -- Census and lifetime of high-mass prestellar cores in 14 massive protoclusters
• The ALMA Survey of 70 $\mu$m Dark High-mass Clumps in Early Stages (ASHES). XII. Unanchored Forked Stream in the Propagating Path of a Protostellar Outflow
• Interaction between the Supernova Remnant W44 and the Infrared Dark Cloud G034.77-00.55: shock induced star formation?
• Impeding Turbulence Decay in Self-gravitating Cloud Cores
• Chemical complexity in star formation induced by stellar feedback: cores shock-formed by the supernova remnant W44
• Chemistry of Dark Molecular Clouds