Mother of dragons: A massive, quiescent core in the dragon cloud (IRDC G028.37+00.07)
Journal article, 2023
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 clouda'(also known as G028.37+00.07 or Cloud Ca). This core (C2c1) sits at the end of a chain of a roughly equally spaced actively star-forming cores near the center 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 M· and 2 M· (31 M· and 6 M· without background subtraction), respectively. The cores do not appear to fragment further on the scales of our highest-angular-resolution images (0.2 , 0.005 pc ∼ 1000 AU). We find that these cores are very dense (nH2 > 106 cm-3) and have only trans-sonic non-thermal motions ( 3s ∼ 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.
ISM: structure
ISM: clouds
Stars: formation
Stars: massive
Author
Ashley T. Barnes
University of Bonn
European Southern Observatory (ESO)
Junhao Liu
East Asian Observatory
Q. Zhang
Harvard-Smithsonian Center for Astrophysics
Jonathan Tan
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
University of Virginia
F. Bigiell
University of Bonn
P. Caselli
Max Planck Society
Giuliana Cosentino
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Francesco Fontani
Arcetri Astrophysical Observatory
Jonathan D. Henshaw
Liverpool John Moores University
Max Planck Society
I. Jimenez-Serra
Instituto Nacional de Tecnica Aeroespacial
D. S. Kalb
Max Planck Society
Chi Yan Law
European Southern Observatory (ESO)
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
S. Longmore
Liverpool John Moores University
R. J. Parker
University of Sheffield
J. Pineda
Max Planck Society
A. Sanchez-Monge
Spanish National Observatory (OAN)
Wanggi Lim
California Institute of Technology (Caltech)
Ke Wang
Beijing University of Technology
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 675 A53Subject Categories
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Other Physics Topics
Probability Theory and Statistics
DOI
10.1051/0004-6361/202245668