Digging into the Interior of Hot Cores with ALMA (DIHCA). I. Dissecting the High-mass Star-Forming Core G335.579-0.292 MM1

TL;DR

This study uses high-resolution ALMA observations to dissect the complex gas dynamics and fragmentation within a massive star-forming core, revealing infall, expansion, and rotation motions that inform high-mass star formation processes.

Contribution

The paper provides detailed kinematic analysis of a high-mass star-forming core at 1000 au resolution, highlighting the interplay of infall, expansion, and rotation in the core's evolution.

Findings

Detection of multiple fragments within G335-MM1

Evidence of infall and expansion motions near the core center

Identification of a rotating source with a 10-30 M_sun system mass

Abstract

We observed the high-mass star-forming region G335.579-0.292 with the Atacama Large Millimeter/submillimeter Array (ALMA) at 226 GHz with an angular resolution of 0.3'' ($\sim 1000$ au resolution at the source distance). G335.579-0.292 hosts one of the most massive cores in the Galaxy (G335-MM1). The continuum emission shows that G335-MM1 fragments into at least five sources, while molecular line emission is detected in two of the continuum sources (ALMA1 and ALMA3). We found evidence of large and small scale infall in ALMA1 revealed by an inverse P-Cygni profile and the presence of a blue-shifted spot at the center of the first moment map of the CH$_3$CN emission. In addition, hot gas expansion in the innermost region is unveiled by a red-shifted spot in the first moment map of HDCO and (CH$_3$)$_2$CO (both with $E_u > 1100$ K). Our modeling reveals that this expansion motion originates close to the central source, likely due to reversal of the accretion flow induced by the expansion of the HII region, while infall and rotation motions originate in the outer regions. ALMA3 shows clear signs of rotation, with a rotation axis inclination with respect to the line of sight close to $90^\circ$, and a system mass (disk + star) in the range of 10-30 M$_\odot$.