Fragmenting Filaments in the DR21 Ridge

The Stellar Nursery Observation Initiative presents a detailed, multi-scale investigation of the DR21 Ridge, one of the most active high-mass star-forming regions in the Milky Way. Using high-resolution ALMA observations, this research reveals how large molecular filaments fragment into dense cores, driving the birth of massive stars through complex accretion and dynamical processes.

Observations: ALMA Mapping of the DR21 Filament Network

ALMA’s millimeter and sub-millimeter observations resolve the DR21 Ridge across multiple spatial scales, from parsec-length filaments down to compact protostellar cores. These data allow direct tracing of gas density, velocity structure, and fragmentation patterns within a massive star-forming environment.

Filamentary Gas Structure

The DR21 Ridge is composed of interconnected filaments funneling material toward central hubs. These filaments act as mass reservoirs, continuously feeding dense regions where star formation is concentrated.
Velocity Gradients and Gas Flows

Observed velocity gradients along filaments indicate large-scale gas inflow toward the ridge center, confirming that high-mass star formation is sustained by ongoing accretion rather than isolated collapse.

Analysis I: Hierarchical Fragmentation and Core Formation

Filament Fragmentation into Dense Cores

The DR21 filament undergoes hierarchical fragmentation, breaking into clumps and then into gravitationally bound cores. Many of these cores exceed the mass threshold required to form high-mass stars.
Core Spacing and Instability Signatures

Core separations are consistent with gravitational instability models, suggesting that turbulence and self-gravity jointly regulate fragmentation scales within massive filaments.

Analysis II: Accretion Dynamics and High-Mass Star Growth

Multi-Scale Accretion Flows

Gas accretion operates simultaneously at filament, clump, and core scales. This continuous inflow enables protostars to grow rapidly despite strong radiation feedback.
Early Feedback and Outflow Signatures

Collimated molecular outflows detected in several cores mark the onset of stellar feedback, influencing nearby fragmentation while not halting global accretion.

Discussion: Rethinking High-Mass Star Formation

The DR21 Ridge demonstrates that high-mass star formation is a collective, dynamic process driven by filamentary accretion rather than isolated monolithic collapse. These findings bridge the gap between turbulent core models and competitive accretion scenarios.

Conclusion: Filaments as Engines of Massive Star Birth

The Stellar Nursery Observation Initiative shows that fragmenting filaments play a central role in regulating mass flow, fragmentation, and accretion in high-mass star-forming regions. DR21 serves as a benchmark for understanding massive star formation across the galaxy.

About the Researchers