From the Convergence of Filaments to Disk-Outflow Accretion: Massive-Star Formation in W33A

TL;DR

This study uses high-resolution interferometric observations to reveal filamentary structures, core evolution, and disk-outflow dynamics in the massive star-forming region W33A, supporting models of filament convergence and disk-mediated accretion.

Contribution

It provides detailed observational evidence of filament convergence, core differentiation, and disk-outflow systems in a massive star formation region, advancing understanding of star formation processes.

Findings

Detection of intersecting filamentary structures triggering star formation.

Identification of multiple condensations within cores at different evolutionary stages.

Evidence of a rotating disk and associated outflow around a massive protostar.

Abstract

Interferometric observations of the W33A massive star-formation region, performed with the Submillimeter Array (SMA) and the Very Large Array (VLA) at resolutions from 5 arcsec (0.1 pc) to 0.5 arcsec (0.01 pc) are presented. Our three main findings are: (1) parsec-scale, filamentary structures of cold molecular gas are detected. Two filaments at different velocities intersect in the zone where the star formation is occurring. This is consistent with triggering of the star-formation activity by the convergence of such filaments, as predicted by numerical simulations of star formation initiated by converging flows. (2) The two dusty cores (MM1 and MM2) at the intersection of the filaments are found to be at different evolutionary stages, and each of them is resolved into multiple condensations. MM1 and MM2 have markedly different temperatures, continuum spectral indices, molecular-line spectra, and masses of both stars and gas. (3) The dynamics of the "hot-core" MM1 indicates the presence of a rotating disk in its center (MM1-Main) around a faint free-free source. The stellar mass is estimated to be approximately 10 Msun. A massive molecular outflow is observed along the rotation axis of the disk.