Insights on Gas Distribution and Dynamics in Massive Proto-cluster G358.46$-$0.39: Possible Multiplicity in G358.46$-$0.39 MM1a

TL;DR

This study uses ALMA data to analyze gas distribution, outflows, and potential multiplicity in the massive proto-cluster G358.46-0.39, revealing complex dynamics and signs of active star formation in core MM1a.

Contribution

It provides detailed molecular and kinematic analysis of G358.46-0.39, highlighting possible multiplicity and outflow structures in MM1a with high-resolution observations.

Findings

Filamentary and dumbbell-shaped gas structures from HII region expansion.

Overlapped outflow lobes suggest multiple YSOs in MM1a.

Evidence of rotation and active accretion in MM1a.

Abstract

This work explored the spatial distribution of C$^{17}$O, SiO, HC$_{3}$N and SO$_{2}$ molecules, as well as the energetics of outflows in G358.46$-$0.39 proto-cluster using ALMA band 7 archival data, with the aim of providing an improved understanding of its protostellar nature, gas kinematics and dynamics. G358.46$-$0.39 is previously known to consist of 4 dust continuum cores (MM1a, MM1b, MM1c and MM2). The integrated intensity map of C$^{17}$O reveals filamentary and dumbbell-shaped structures that are probably compressed gases from the expansion of the HII region MM2. The SiO emission reveals spatially overlapped blue and red outflow lobes, likely driven by an unresolved young stellar object (YSO) in MM1a. The spatial distribution of HC$_{3}$N and SO$_{2}$ molecules in MM1a shows a compact morphology, with no detectable HC$_{3}$N and SO$_{2}$ emissions in the other cores. The SO$_{2}$ emission reveals a clear velocity gradient in MM1a, as well as large velocity dispersion ($\sim$ 3\,\kms) within the inner core of MM1a, which are consistent with rotating structures. We estimated the mass, momentum and energy outflow rate, as well as other outflow parameters. The SiO outflow exhibits a different morphology compared to the $^{12}$CO outflow morphology previously observed in MM1a. The SiO and $^{12}$CO outflows are probably associated with disks of separate cores with one face-on and the other edge-on, pointing to multiplicity of YSOs in MM1a. The properties of MM1a indicate that it is a massive protostar that is actively accreting and undergoing star formation.