Mother of dragons

• Published in: Astronomy and astrophysics (Berlin) 2023-07, Vol.675
• Main Authors: Barnes, A T, Liu, J, Zhang, Q, Tan, J C, Bigiel, F, Caselli, P, Cosentino, G, Fontani, F, Henshaw, J D, Jiménez-Serra, I, D.-S. Kalb, Law, C Y, Longmore, S N, Parker, R J, Pineda, J E, Sánchez-Monge, A, Lim, W, Wang, K
• Format: Article
• Language: English
• Subjects: Astronomical models; Deposition; Infrared analysis; Massive stars; Molecular clouds; Star & galaxy formation; Star formation; Stellar cores; Subtraction
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/202245668

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 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 (ℳs ~ 1). Together the mass, density, and internal motions imply a virial parameter of