Isolated Massive Star Formation in G28.20-0.05

Abstract

We report high-resolution 1.3~mm continuum and molecular line observations of the massive protostar G28.20-0.05 with ALMA. The continuum image reveals a ring-like structure with 2,000~au radius, similar to morphology seen in archival 1.3~cm VLA observations. Based on its spectral index and associated H$30\alpha$ emission, this structure mainly traces ionised gas. However, there is evidence for $\sim 30$~M${}_{\odot }$ of dusty gas near the main mm continuum peak on one side of the ring, as well as in adjacent regions within 3,000~au. A virial analysis on scales of $\sim$2,000~au from hot core line emission yields a dynamical mass of $\sim 80M_{\odot }$. A strong velocity gradient in the H$30\alpha$ emission is evidence for a rotating, ionized disk wind, which drives a larger-scale molecular outflow. An infrared SED analysis indicates a current protostellar mass of $m_{\ast }\sim 40M_{\odot }$ forming from a core with initial mass $M_c\sim 300M_{\odot }$ in a clump with mass surface density of ${\Sigma }_{\mathrm{cl}}\sim 0.8{\mathrm{g}\mathrm{cm}}^{-2}$. Thus the SED and other properties of the system can be understood in the context of core accretion models. Structure-finding analysis on the larger-scale continuum image indicates G28.20-0.05 is forming in a relatively isolated environment, with no other concentrated sources, i.e., protostellar cores, above $\sim 1M_{\odot }$ found from $\sim$0.1 to 0.4~pc around the source. This implies that a massive star can form in relative isolation and the dearth of other protostellar companions within the $\sim 1$~pc environs is a strong constraint on massive star formation theories that predict the presence of a surrounding protocluster.

Accepted to ApJ

References in corpus (13)

• Array Programming with NumPy
• Structural Analysis of Molecular Clouds: Dendrograms
• The Fragmentation of Magnetized, Massive Star-Forming Cores with Radiative Feedback
• Radiation Transfer of Models of Massive Star Formation. IV. The Model Grid and Spectral Energy Distribution Fitting
• Internal Dynamics of the Hypercompact H II Region G28.20-0.04N
• Dynamics of a Massive Binary at Birth
• The SOFIA Massive (SOMA) Star Formation Survey. II. High Luminosity Protostars
• Discovery of a Photoionized Bipolar Outflow towards the Massive Protostar G45.47+0.05
• Massive Protostars in a Protocluster -- A Multi-Scale ALMA View of G35.20-0.74N
• The Core Mass Function Across Galactic Environments. III. Massive Protoclusters
• Ultracompact H II Regions with Extended Emission: The Complete View
• High-Resolution Observations of Molecular Lines toward the Hot Core G28.20-0.04N
• Deuterium Chemodynamics of Massive Pre-Stellar Cores

Cited by in corpus (5)

• The SOFIA Massive (SOMA) Star Formation Survey. IV. Isolated Protostars
• Massive Prestellar Cores in Radiation-magneto-turbulent Simulations of Molecular Clouds
• X3: a high-mass Young Stellar Object close to the supermassive black hole Sgr~A*
• Near-Infrared Observations of Outflows and YSOs in the Massive Star-Forming Region AFGL 5180
• The SOFIA Massive (SOMA) Star Formation Q-band Follow-up. II. Hydrogen Recombination Lines Toward High-Mass Protostars