title: Self-similar fragmentation regulated by magnetic fields in a region forming massive stars.
abstract: Most molecular clouds are filamentary or elongated. For those forming low-mass stars (<8 solar masses), the competition between self-gravity and turbulent pressure along the dynamically dominant intercloud magnetic field (10 to 100 parsecs) shapes the clouds to be elongated either perpendicularly or parallel to the fields. A recent study also suggested that on the scales of 0.1 to 0.01 parsecs, such fields are dynamically important within cloud cores forming massive stars (>8 solar masses). But whether the core field morphologies are inherited from the intercloud medium or governed by cloud turbulence is unknown, as is the effect of magnetic fields on cloud fragmentation at scales of 10 to 0.1 parsecs. Here we report magnetic-field maps inferred from polarimetric observations of NGC 6334, a region forming massive stars, on the 100 to 0.01 parsec scale. NGC 6334 hosts young star-forming sites where fields are not severely affected by stellar feedback, and their directions do not change much over the entire scale range. This means that the fields are dynamically important. The ordered fields lead to a self-similar gas fragmentation: at all scales, there exist elongated gas structures nearly perpendicular to the fields. Many gas elongations have density peaks near the ends, which symmetrically pinch the fields. The field strength is proportional to the 0.4th power of the density, which is an indication of anisotropic gas contractions along the field. We conclude that magnetic fields have a crucial role in the fragmentation of NGC 6334.
authors.affiliation: Department of Physics, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong, China.
authors.forename: Hua-bai
authors.initials: HB
authors.lastname: Li
authors.affiliation: Department of Physics, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong, China.
authors.forename: Ka Ho
authors.initials: KH
authors.lastname: Yuen
authors.affiliation: Department of Physics, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong, China.
authors.forename: Frank
authors.initials: F
authors.lastname: Otto
authors.affiliation: Department of Physics, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong, China.
authors.forename: Po Kin
authors.initials: PK
authors.lastname: Leung
authors.affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Sridharan
authors.affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA.
authors.forename: Qizhou
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Academia Sinica Institute of Astronomy and Astrophysics, 11F Astronomy-Mathematics Building, AS/NTU (National Taiwan University) No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan, China.
authors.forename: Hauyu
authors.initials: H
authors.lastname: Liu
authors.affiliation: Academia Sinica Institute of Astronomy and Astrophysics, 11F Astronomy-Mathematics Building, AS/NTU (National Taiwan University) No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan, China.
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Tang
authors.affiliation: School of Astronomy and Space Science, Nanjing University, 22 Hankou Road, Nanjing, Jiangsu 210093, China.
authors.forename: Keping
authors.initials: K
authors.lastname: Qiu
references.citation: Science. 2006 Aug 11;313(5788):812-4
references.pmid: 16902132