Magnetic Fields and Fragmentation of Filaments in the Hub of California-X

Abstract

We present 850 $\mu$m polarization and ${\mathrm{C}}^{18}\mathrm{O}(3-2)$ molecular line observations toward the X-shaped nebula in the California molecular cloud using the JCMT SCUBA-2/POL-2 and HARP instruments. The 850 $\mu$m emission shows that the observed region includes two elongated filamentary structures (Fil1 and Fil2) having chains of regularly spaced cores. We measured the mass per unit length of the filament and found that Fil1 and Fil2 are thermally super- and subcritical, respectively, but both are subcritical if nonthermal turbulence is considered. The mean projected spacings ($\Delta \bar{S}$) of cores in Fil1 and Fil2 are 0.13 and 0.16 pc, respectively. $\Delta \bar{S}$ are smaller than $4\times$filament width expected in the classical cylinder fragmentation model. The large-scale magnetic field orientations shown by Planck are perpendicular to the long axes of Fil1 and Fil2, while those in the filaments obtained from the high-resolution polarization data of JCMT are disturbed, but those in Fil1 tend to have longitudinal orientations. Using the modified Davis-Chandrasekhar-Fermi (DCF) method, we estimated the magnetic field strengths ($B_{\mathrm{pos}}$) of filaments which are 110$\pm$80 and 90$\pm$60 $\mu$G. We calculated the gravitational, kinematic, and magnetic energies of the filaments, and found that the fraction of magnetic energy is larger than 60 % in both filaments. We propose that a dominant magnetic energy may lead the filament to be fragmented into aligned cores as suggested by Tang et al., and a shorter core spacing can be due to a projection effect via the inclined geometry of filaments or due to a non-negligible, longitudinal magnetic fields in case of Fil1.

Accepted for publication in the ApJ. 18 pages, 11 figures, 2 tables

References in corpus (27)

• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• Filamentary structure of star-forming complexes
• A Large Catalog of Accurate Distances to Local Molecular Clouds: The Gaia DR2 Edition
• Unifying low and high mass star formation through density amplified hubs of filaments
• Chains of dense cores in the Taurus L1495/B213 complex
• FellWalker - a Clump Identification Algorithm
• The JCMT BISTRO Survey: The magnetic field strength in the Orion A filament
• ALMA observations of dust polarization and molecular line emission from the Class 0 protostellar source Serpens SMM1
• Magnetized filamentary gas flows feeding the young embedded cluster in Serpens South
• Dust polarized emission observations of NGC 6334; BISTRO reveals the details of the complex but organized magnetic field structure of the high-mass star-forming hub-filament network
• Gravity, Magnetic Field, and Turbulence: Relative Importance and Impact on Fragmentation in the Infrared Dark Cloud G34.43+00.24
• A Decade of SCUBA-2: A Comprehensive Guide to Calibrating 450 $\mu$m and 850 $\mu$m Continuum Data at the JCMT
• Grain alignment and disruption by radiative torques in dense molecular clouds and implication for polarization holes
• The JCMT BISTRO Survey: The Magnetic Field of the Barnard 1 Star-Forming Region
• The JCMT BISTRO Survey: The Magnetic Field In The Starless Core $\rho$ Ophiuchus C
• B-fields in Star-Forming Region Observations (BISTRO): Magnetic Fields in the Filamentary Structures of Serpens Main
• Revealing the diverse magnetic field morphologies in Taurus dense cores with sensitive sub-millimeter polarimetry
• Fragmentation of star-forming filaments in the X-shape Nebula of the California molecular cloud
• The JCMT BISTRO Survey: A Spiral Magnetic Field in a Hub-filament Structure, Monoceros R2
• Observations of magnetic fields surrounding LkH$\alpha$ 101 taken by the BISTRO survey with JCMT-POL-2
• The JCMT BISTRO-2 Survey: Magnetic Fields of the Massive DR21 Filament
• Fragmentation of Filamentary Cloud Permeated by Perpendicular Magnetic Field
• Simultaneous evidence of edge collapse and hub-filament configurations: A rare case study of a Giant Molecular Filament G45.3+0.1
• The JCMT BISTRO Survey: An 850/450$\mu$m Polarization Study of NGC 2071IR in OrionB
• TRAO Survey of Nearby Filamentary Molecular clouds, the Universal Nursery of Stars (TRAO FUNS) I. Dynamics and Chemistry of L1478 in the California Molecular Cloud
• Evolution of the Hub-filament Structures in IC 5146 in the Context of the Energy Balance of Gravity, Turbulence, and Magnetic Field
• Velocity-Coherent Substructure in TMC-1: Inflow and Fragmentation

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