ALMA resolves the spiraling accretion flow in the luminous OB cluster forming region G33.92+0.11

Abstract

How rapidly collapsing parsec-scale massive molecular clumps feed high-mass stars, and how they fragment to form OB clusters, have been outstanding questions in the field of star-formation. In this work, we report the resolved structures and kinematics of the approximately face-on, rotating massive molecular clump, G33.92+0.11. Our high resolution Atacama Large Millimeter/submillimeter Array (ALMA) images show that the spiral arm-like gas overdensities form in the eccentric gas accretion streams. First, we resolved that the dominant part of the $\sim$0.6 pc scale massive molecular clump (3.0${}_{-1.4}^{+2.8}$$\cdot$10${}^3$ $M_{\odot }$) G33.92+0.11 A is tangled with several 0.5-1 pc size molecular arms spiraling around it, which may be connected further to exterior gas accretion streams. Within G33.92+0.11 A, we resolved the $\sim$0.1 pc width gas mini-arms connecting with the two central massive (100-300 $M_{\odot }$) molecular cores. The kinematics of arms and cores elucidate a coherent accretion flow continuing from large to small scales. We demonstrate that the large molecular arms are indeed the cradles of dense cores, which are likely current or future sites of high-mass star formation. Since these deeply embedded massive molecular clumps preferentially form the highest mass stars in the clusters, we argue that dense cores fed by or formed within molecular arms play a key role in making the upper end of the stellar and core mass functions.

20 pages, formally published by ApJ

References in corpus (5)

• Filamentary structure of star-forming complexes
• Molecular Cloud Evolution II. From cloud formation to the early stages of star formation in decaying conditions
• Gravitational fragmentation and the formation of brown dwarfs in stellar clusters
• Formation of Magnetized Prestellar Cores with Ambipolar Diffusion and Turbulence
• Core and filament formation in magnetized, self-gravitating isothermal layers

Cited by in corpus (6)

• Rotation in young massive star clusters
• Cloud Structure of Galactic OB Cluster Forming Regions from Combining Ground and Space Based Bolometric Observations
• Magnetically Dominated Parallel Interstellar Filaments at the Infrared Dark Cloud G14.225-0.506
• Revealing a spiral-shaped molecular cloud in our galaxy - Cloud fragmentation under rotation and gravity
• Interpreting observations of edge-on gravitationally unstable accretion flows
• Comparing binary systems from rotating parent gas structures with different total masses