Magnetized interstellar molecular clouds – II. The large-scale structure and dynamics of filamentary molecular clouds

Journal Article · Wed Mar 27 00:00:00 EDT 2019 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stz653· OSTI ID:1606597

Li, Pak Shing ^[1]; Klein, Richard I. ^[2]

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1. Astronomy Department, University of California, Berkeley, CA 94720, USA
2. Astronomy Department, University of California, Berkeley, CA 94720, USA, Lawrence Livermore National Laboratory, PO Box 808, L-23, Livermore, CA 94550, USA

Abstract

We perform ideal magnetohydrodynamics high-resolution adaptive mesh refinement simulations with driven turbulence and self-gravity and find that long filamentary molecular clouds are formed at the converging locations of large-scale turbulence flows and the filaments are bounded by gravity. The magnetic field helps shape and reinforce the long filamentary structures. The main filamentary cloud has a length of ∼4.4 pc. Instead of a monolithic cylindrical structure, the main cloud is shown to be a collection of fibre/web-like substructures similar to filamentary clouds such as L1495. Unless the line-of-sight is close to the mean field direction, the large-scale magnetic field and striations in the simulation are found roughly perpendicular to the long axis of the main cloud, similar to L1495. This provides strong support for a large-scale moderately strong magnetic field surrounding L1495. We find that the projection effect from observations can lead to incorrect interpretations of the true three-dimensional physical shape, size, and velocity structure of the clouds. Helical magnetic field structures found around filamentary clouds that are interpreted from Zeeman observations can be explained by a simple bending of the magnetic field that pierces through the cloud. We demonstrate that two dark clouds form a T-shaped configuration that is strikingly similar to the infrared dark cloud SDC13, leading to the interpretation that SDC13 results from a collision of two long filamentary clouds. We show that a moderately strong magnetic field ($${{\cal M}_{\rm A}}\sim 1$$) is crucial for maintaining a long and slender filamentary cloud for a long period of time ∼0.5 Myr.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: Extreme Science and Engineering Discovery Environment (XSEDE); National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); USDOE; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC)
• Grant/Contract Number: AC02-05CH11231; AC52-07NA27344
• OSTI ID: 1606597
• Alternate ID(s): OSTI ID: 1884650
• Report Number(s): LLNL-JRNL-760296
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 4 Vol. 485; ISSN 0035-8711
• Publisher: Oxford University Press
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
clouds
evolution
kinematics and dynamics
magnetic fields
methods
numerical
turbulence