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Most molecular clouds are filamentary or elongated. Among those forming low-mass stars, their long axes tend to be either parallel or perpendicular to the large-scale (10-100 pc) magnetic field (B-field) in the surrounding inter cloud…

Astrophysics of Galaxies · Physics 2015-10-27 Hua-bai Li , Ka Ho Yuen , Frank Otto , Po Kin Leung , T. K. Sridharan , Qizhou Zhang , Hauyu Liu , Ya-Wen Tang , Keping Qiu

Supersonic random motions are observed in dark clouds and are traditionally interpreted as Alfven waves, but the possibility that these motions are super-Alfvenic has not been ruled out. In this work we report the results of numerical…

Astrophysics · Physics 2009-10-31 Paolo Padoan , AAke Nordlund

We present synthetic OH Zeeman splitting measurements of a super-Alfvenic model of molecular clouds. We select dense cores from synthetic 13CO maps computed from the largest simulation to date of supersonic and super-Alfvenic turbulence.…

Astrophysics · Physics 2016-08-14 Tuomas Lunttila , Paolo Padoan , Mika Juvela , Åke Nordlund

We present an analysis of the relationship between the orientation of magnetic fields and filaments that form in 3D magnetohydrodynamic simulations of cluster-forming, turbulent molecular cloud clumps. We examine simulated cloud clumps with…

Astrophysics of Galaxies · Physics 2016-12-21 Mikhail Klassen , Ralph E. Pudritz , Helen Kirk

We study the magnetic field to density ($B-\rho$) relation in turbulent molecular clouds with dynamically important magnetic fields using nonideal three-dimensional magnetohydrodynamic simulations. Our simulations show that there is a…

Astrophysics of Galaxies · Physics 2022-03-30 Sayantan Auddy , Shantanu Basu , Takahiro Kudoh

Magnetic fields and turbulence may play a crucial role in the evolution of molecular clouds and ultimately in the formation of dense cores and stars. Despite being studied in many molecular clouds, the exact role of magnetic fields and…

Astrophysics of Galaxies · Physics 2026-03-26 A. Koley , P. Sanhueza , A. M. Stutz , P. Saha , F. A. Olguin , A. Ginsburg , N. Sandoval-Garrido , N. Castro-Toledo

Recent observational evidence that magnetic fields are dynamically important in molecular clouds, compared to self-gravity and turbulence, is reviewed and illustrated with data from the NGC 2024 region. One piece of evidence, turbulence…

Astrophysics of Galaxies · Physics 2015-05-19 Hua-bai Li , Raymond Blundell , Abigail Hedden , Jonathan Kawamura , Scott Paine , Edward Tong

We expand our study on the dispersion of polarization angles in molecular clouds. We show how the effect of signal integration through the thickness of the cloud as well as across the area subtended by the telescope beam inherent to dust…

Astrophysics of Galaxies · Physics 2014-11-20 Martin Houde , John E. Vaillancourt , Roger H. Hildebrand , Shadi Chitsazzadeh , Larry Kirby

We present a set of numerical experiments designed to systematically investigate how turbulence and magnetic fields influence the morphology, energetics, and dynamics of filaments produced in wind-cloud interactions. We cover 3D…

Astrophysics of Galaxies · Physics 2017-12-06 Wladimir Banda-Barragán , Christoph Federrath , Roland Crocker , Geoffrey Bicknell

How important is the magnetic (B-) field when compared to gravity and turbulence in the star-formation process? Does its importance depend on scale and location? We summarize submm dust polarization observations towards the large…

We present a set of numerical simulations addressing the effects of magnetic field strength and orientation on the flow-driven formation of molecular clouds. Fields perpendicular to the flows sweeping up the cloud can efficiently prevent…

Astrophysics · Physics 2011-02-11 F. Heitsch , J. M. Stone , L. W. Hartmann

Magnetic fields pervade in the interstellar medium (ISM) and are believed to be important in the process of star formation, yet probing magnetic fields in star formation regions is challenging. We propose a new method to use Faraday…

Astrophysics of Galaxies · Physics 2018-06-27 M. Tahani , R. Plume , J. C. Brown , J. Kainulainen

Star formation in our Galaxy occurs in molecular clouds that are self-gravitating, highly turbulent, and magnetized. We study the conditions under which cloud cores inherit large-scale magnetic field morphologies and how the field is…

Astrophysics of Galaxies · Physics 2017-03-29 Philip Mocz , Blakesley Burkhart , Lars Hernquist , Chris McKee , Volker Springel

We examine the effects of self-gravity and magnetic fields on supersonic turbulence in isothermal molecular clouds with high resolution simulations and adaptive mesh refinement. These simulations use large root grids (512^3) to capture…

Solar and Stellar Astrophysics · Physics 2015-06-04 David Collins , Alexei G. Kritsuk , Paolo Padoan , Hui Li , Hao Xu , Sergey D. Ustyugov , Michael L. Norman

We report here observations of the Zeeman effect in the 18-cm lines of OH in the envelope regions surrounding four molecular cloud cores toward which detections of B(LOS) have been achieved in the same lines, and evaluate the ratio of mass…

Astrophysics · Physics 2011-02-11 Richard M. Crutcher , Nicholas Hakobian , Thomas H. Troland

During the past decade the dynamical importance of magnetic fields in molecular clouds has been increasingly recognized, as observational evidence has accumulated. However, how a magnetic field affect star formation is still unclear.…

Astrophysics of Galaxies · Physics 2020-09-15 C. Y. Law , H. -b. Li , Z. Cao , C. -Y. Ng

We analyse extinction maps of nearby Giant Molecular Clouds to forge a link between driving processes of turbulence and modes of star formation. Our investigation focuses on cloud structure in the column density range above the self…

Astrophysics of Galaxies · Physics 2015-05-28 J. Rowles , D. Froebrich

The most accurate measurements of magnetic fields in star-forming gas are based on the Zeeman observations analyzed by Crutcher et al. (2010). We show that their finding that the 3D magnetic field scales approximately as density$^{0.65}$…

Astrophysics of Galaxies · Physics 2015-08-06 Pak Shing Li , Christopher F. McKee , Richard I. Klein

The formation of molecular clouds, which serve as stellar nurseries in galaxies, is poorly understood. A class of cloud formation models suggests that a large-scale galactic magnetic field is irrelevant at the scale of individual clouds,…

Astrophysics of Galaxies · Physics 2011-11-14 Hua-bai Li , Thomas Henning

We present a detailed study of the Cep B molecular cloud based on sub-mm dust polarization and $^{13}$CO (J=3--2) spectral line observations obtained with SCUBA-2/POL-2 and HARP on the James Clerk Maxwell Telescope (JCMT). The 850 $\mu$m…