The birth of stars is a complex and inefficient process, and scientists are still unraveling the mysteries behind it. One intriguing aspect of star formation is the role of filamentary structures within giant molecular clouds (GMCs). These filaments, as revealed by recent research, play a crucial role in channeling gas towards the site of star formation, but they also contribute to the inefficiency of the process.
The study, published in The Astrophysical Journal Letters, delves into the formation of hub-filament systems (HFSs), which are characterized by multiple filaments aligned radially towards a central high-density hub. These systems are observed in star-forming regions and have puzzled scientists due to their unique structure.
Shingo Nozaki and Shu-ichiro Inutsuka, the authors of the research, used ATERUI III, a powerful supercomputer, to run hydrodynamical simulations. They modeled the interaction between a molecular cloud and an external shock, simulating the impact of a supernova remnant. The initial condition was a flattened GMC, and the key insight came from the hourglass-shaped magnetic fields detected in star-forming regions by ALMA.
Before the shock reached the cloud, the magnetic field aligned with the z-axis became pinched near the center due to gravitational contraction, forming a weak hourglass-shaped morphology. As the shock wave struck different parts of the GMC at various times, it strengthened certain parts of the magnetic field, creating the filaments. Star-forming gas then flowed along these filaments, converging into a central hub where stars were born.
The simulations revealed that the kinematic segregation within the filaments limits the rapid mass supply to the central dense region, preventing an excessively high star formation efficiency (SFE). The estimated SFE is 4%, which aligns with observations of nearby molecular clouds. However, the potential SFE in filamentary gas is only 0.7%, highlighting the inefficiency of star formation within these structures.
This research provides valuable insights into the complex interplay between gas, magnetic fields, and shocks during star formation. It suggests that the hourglass-shaped magnetic fields and the resulting filamentary networks are essential in regulating the efficiency of star formation. The authors emphasize that the specific nature of the shock is not the sole determining factor, but rather the cycle of life and death of stars that shapes the next generation of stellar cradles.
