ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions $-$ XVII. High-mass star-formation through a large-scale collapse in IRAS 15394$-$5358

TL;DR

This study uses ALMA data to analyze the structure and dynamics of a massive star-forming region, revealing a hub-filament system undergoing global collapse that supports high-mass star formation.

Contribution

It provides detailed observational evidence of large-scale collapse and fragmentation in a high-mass star-forming protocluster, highlighting the role of hub-filament systems.

Findings

Massive clump fragments into six cores with thermal Jeans fragmentation.

Cores are gravitationally bound with small virial parameters.

Velocity gradients indicate global collapse feeding the hub.

Abstract

Hub-filament systems are considered as natural sites for high-mass star formation. Kinematic analysis of the surroundings of hub-filaments is essential to better understand high-mass star formation within such systems. In this work, we present a detailed study of the massive Galactic protocluster IRAS 15394$-$5358, using continuum and molecular line data from the ALMA Three-millimeter Observations of Massive Star-forming Regions (ATOMS) survey. The 3~mm dust continuum map reveals the fragmentation of the massive ($\rm M=843~M_{\odot}$) clump into six cores. The core C-1A is the largest (radius = 0.04~pc), the most massive ($\rm M=157~M_{\odot}$), and lies within the dense central region, along with two smaller cores ($\rm M=7~and~3~M_{\odot}$). The fragmentation process is consistent with the thermal Jeans fragmentation mechanism and virial analysis shows that all the cores have small virial parameter values ($\rm \alpha_{vir}<<2$), suggesting that the cores are gravitationally bound. The mass vs. radius relation indicates that three cores can potentially form at least a single massive star. The integrated intensity map of $\rm H^{13}CO^{+}$ shows that the massive clump is associated with a hub-filament system, where the central hub is linked with four filaments. A sharp velocity gradient is observed towards the hub, suggesting a global collapse where the filaments are actively feeding the hub. We discuss the role of global collapse and the possible driving mechanisms for the massive star formation activity in the protocluster.