Shanghai Astronomical Observatory Astrophysics Colloquium

Title：The Role of Magnetic Fields in the Stability and Fragmentation of Filamentary Molecular Clouds

Speaker：Pak Shing Li (SHAO)

Location: Lecture Hall, 3rd floor

Time：3:00 pm March. 02th (Thursday)

Abstract：

Long and slender filamentary structures are commonly found inside giant molecular clouds. Filamentary molecular clouds can be more than 10-pc long and some have clumpy structures along the clouds. High resolution imaging of filamentary clouds shows that long filamentary clouds are also composed of smaller filamentary substructures, with some decorated with chains of dense cores. Chain-of-cores and clumpy appearances of some filamentary molecular clouds indicate that these clouds probably are gravitational unstable and are undergoing the fragmentation process at the early stage of star formation. From polarization mapping of magnetic fields around filamentary molecular clouds, observers find that large-scale magnetic fields are generally roughly perpendicular to the long axes of the clouds. Could such magnetic field structures help in supporting filamentary cloud against gravitational collapse? Numerical simulations have been performed to study the formation and the structures of filamentary molecular clouds. In this talk, I present the magnetic field structures of the filamentary molecular clouds in the OMC-3 and OMC-4 regions in Orion A cloud complex and the L1495/B211 region in Taurus cloud complex from our recent polarization mapping using the High-resolution Airborne Wide-band Camera (HAWC+) on NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA). I shall use my numerical simulations on the formation of filamentary molecular clouds to discuss the physical properties of the filamentary clouds in these regions from our stability analysis based on the observed magnetic field structure, column density, and velocity dispersion. We shall see what the role of magnetic fields is in the stability of filamentary clouds in these regions and, with the help of numerical simulation, to find out how viewing angle may affect our interpretation of the physical conditions in molecular clouds.

CV：

Pak-Shing Li is aresearcher at Shanghai Astronomical Observatory. He obtained a PhD degree in 1999 at University of Wyoming. He then did postdoc in National Center for Supercomputing Applications, UCSD and UCB until 2003. Then he joined UC Berkeley as a research specialist until 2023, before he get back and joined SHAO. His research focusses on hydrodynamic simulations, MHD simulations and the study of molecular clouds and star formation. He has developed several famous simulation codes, such as AMRZeus, ZEUS-MP.

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