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.

8+4 pages, 4+2 Figures, 2 Tables, accepted for publication in Astronomy & Astrophysics

References in corpus (23)

• Structural Analysis of Molecular Clouds: Dendrograms
• Filamentary structure of star-forming complexes
• Magnetic Fields in High-Mass Infrared Dark Clouds
• Fragmentation of Molecular Clumps and Formation of Protocluster
• The Origin of Massive Stars: The Inertial-Inflow Model
• The dynamical properties of dense filaments in the infrared dark cloud G035.39-00.33
• 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
• 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
• Unveiling the Early-Stage Anatomy of a Protocluster Hub with ALMA
• The HI/OH/Recombination line survey of the inner Milky Way (THOR): data release 2 and HI overview
• 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
• 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
• 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