Filamentary Flows and Clump-fed High-mass Star Formation in G22

TL;DR

This study investigates the filamentary structures and dynamics in G22, revealing how filamentary flows and clump-scale collapse contribute to high-mass star formation, challenging the necessity of high-mass starless cores.

Contribution

It provides detailed observational evidence of filamentary flows, clump collapse, and core accretion in G22, highlighting simultaneous growth processes in high-mass star formation.

Findings

Velocity gradients along filaments indicate mass inflow.

Clump C1 is in global collapse with significant infall rates.

A hot core with a massive protostar drives outflows and clusters of masers.

Abstract

G22 is a hub-filament system composed of four supercritical filaments. Velocity gradients are detected along three filaments. A total mass infall rate of 440 $M_\odot$~Myr$^{-1}$ would double the hub mass in about six free-fall times. The most massive clump C1 would be in global collapse with an infall velocity of 0.31 km s$^{-1}$ and a mass infall rate of $ 7.2\times10^{-4} $ $M_\odot$ yr$^{-1}$, which is supported by the prevalent HCO$^+$ (3-2) and $^{13}$CO (3-2) blue profiles. A hot molecular core (SMA1) was revealed in C1. At the SMA1 center, there is a massive protostar (MIR1) driving multipolar outflows which are associated with clusters of class I methanol masers. MIR1 may be still growing with an accretion rate of $7\times10^{-5}$ $M_\odot$ yr$^{-1}$. Filamentary flows, clump-scale collapse, core-scale accretion coexist in G22, suggesting that high-mass starless cores may not be prerequisite to form high-mass stars. In the high-mass star formation process, the central protostar, the core, and the clump can grow in mass simultaneously.