Magnetic Fields Versus Gravity

High-mass Star-formation in Filamentary Network

Published: 8th March, 2024, Academia Sinica, Institute of Astronomy & Astrophysics (ASIAA), Taiwan

Banner Image: ESO

The Herschel Space Telescope has discovered that most of the molecular clouds in the Universe exhibit filamentary structures. These high-density filamentary structures are the birth sites of young stars. However, how material transforms from these structures into young stars, and how gravity can overcome the resistance of magnetic fields, remain unanswered questions. In order to shed light on this important step in the formation process of stars, Dr. Jia-Wei Wang, a postdoctoral fellow at the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), has analyzed the magnetic field structure in a massive star-forming region within the NGC 2264 cloud (Figure 1) as part of the B-fields In STar-forming Region Observations (BISTRO) project within a large international collaboration using the James Clerk Maxwell Telescope (JCMT).

NGC 2264 is located in the constellation Monoceros, about 2,700 light-years from Earth. By analyzing the interaction between gravity and magnetic fields, two different types of filamentary structures are identified, each playing a different and distinct role in the process of star formation. One type of filamentary structure is linked to the actual accretion flows and driven by the large-scale gravitational field. This type transports material to higher-density regions along the magnetic field lines (Type-II filament in Figure 2). The other type of filamentary structure receives the accreted material until the local gravitational field grows enough to overcome thermal pressure, turbulence, and magnetic fields (Type-I filament in Figure 2), ultimately igniting the formation of new stars.

"We have found that these two types of filamentary structures provide an explanation of how gravity can overcome magnetic fields. Large-scale gravity is guided by magnetic fields and forming accretion flows, while local smaller-scale gravity within the filaments that accumulate the accreting material, can ignite the formation of massive stars. This discovery can help us understand how the initial stage of massive star formation is determined by the environment,” comments Jia-Wei Wang, who is the leading author of this work.

Fig. 1. NGC 2264 nebula in visible light (left) and in 850 μm radio emission with the JCMT (right). Magnetic field orientations observed with POL-2 on the JCMT are shown with yellow segments, while the large-scale magnetic field inferred from the PLANCK space telescope is shown with green segments. The POL-2 observations show a magnetic field morphology clearly decoupled from the larger-scale PLANCK structures, revealing the detailed star-formation process in a filamentary network. Image credit: ESO/Jia-Wei Wang Team

Fig. 2. (left) Cartoon figure illustrating the proposed scenario of two different types of filaments with filament ridges (green), directions of gravity (red vectors), and magnetic field (yellow segments). Zoom-in figures on the right show the two different types of filaments. Material is accreting along Type-II filaments, driven by gravity and following magnetic field lines. This material is then accumulated onto dense Type-I filaments, where massive star formation takes place (right panels). This is possible through a change in the gravity-magnetic field configuration with respect to the filament ridges, as illustrated with the different alignment between gravity and magnetic field shown with the background color in the zoom-in figures on the right. Image credit: Jia-Wei Wang Team

More Information:

This research presented in a paper "Filamentary Network and Magnetic Field Structures Revealed with BISTRO in the High-mass Star-forming Region NGC 2264: Global Properties and Local Magnetogravitational Configurations,” by Wang, Koch et al. has appeared in the Astrophysical Journal on February 14th, 2024.

Media Contact:

Dr. Jia-Wei Wang   Email:    Tel: +886-2-2366-5459