Digging into the Interior of Hot Cores with ALMA (DIHCA). II. Exploring the Inner Binary (Multiple) System Embedded in G335 MM1 ALMA1

TL;DR

This study uses high-resolution ALMA observations to reveal a complex, multi-source system within a high-mass protostellar core, including a binary, a potential third member, and associated outflow dynamics, advancing understanding of massive star formation.

Contribution

First detailed ALMA imaging of the inner binary system and surrounding structures in G335 MM1, revealing multiple sources, outflow precession, and potential formation mechanisms.

Findings

Discovery of a binary system within G335 MM1

Identification of a bow-like structure possibly forming a third star

Estimation of the primary source's mass as 3.0 M$_\odot$

Abstract

We observed the high-mass protostellar core G335.579-0.272 ALMA1 at ${\sim}200$ au (0.05") resolution with the Atacama Large Millimeter/submillimeter Array (ALMA) at 226 GHz (with a mass sensitivity of $5\sigma=0.2$ M$_\odot$ at 10 K). We discovered that at least a binary system is forming inside this region, with an additional nearby bow-like structure (${\lesssim}1000$ au) that could add an additional member to the stellar system. These three sources are located at the center of the gravitational potential well of the ALMA1 region and the larger MM1 cluster. The emission from CH$_3$OH (and many other tracers) is extended ($>1000$ au), revealing a common envelope toward the binary system. We use CH$_2$CHCN line emission to estimate an inclination angle of the rotation axis of $26^\circ$ with respect to the line of sight based on geometric assumptions and derive a kinematic mass of the primary source (protostar+disk) of 3.0 M$_\odot$ within a radius of 230 au. Using SiO emission, we find that the primary source drives the large scale outflow revealed by previous observations. Precession of the binary system likely produces a change in orientation between the outflow at small scales observed here and large scales observed in previous works. The bow structure may have originated by entrainment of matter into the envelope due to widening or precession of the outflow, or, alternatively, an accretion streamer dominated by the gravity of the central sources. An additional third source, forming due to instabilities in the streamer, cannot be ruled out as a temperature gradient is needed to produce the observed absorption spectra.