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The magnetic field structure in the multi-source magnetized core NGC 2024 FIR 5

Published online by Cambridge University Press:  01 November 2008

Felipe de O. Alves
Affiliation:
Institut de Ciències de l'Espai (IEEC–CSIC), Bellaterra, Catalunya 08193, Spain email: oliveira@ieec.uab.es
J. M. Girart
Affiliation:
Institut de Ciències de l'Espai (IEEC–CSIC), Bellaterra, Catalunya 08193, Spain email: oliveira@ieec.uab.es
S.-P. Lai
Affiliation:
Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30043, Taiwan email: slai@phys.nthu.edu.tw
R. Rao
Affiliation:
Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23–141, Taipei 10617, Taiwan email: rrao@sma.hawaii.edu
Q. Zhang
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA email: qzhang@cfa.harvard.edu
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Abstract

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This work reports high resolution SMA polarimetric observations toward NGC 2024 FIR 5, a magnetized core previously found to harbour protostars. Our 345 GHz data indicates the presence of an extended dust emission associated with the dense core where the protostars are embedded. The 3σ polarized intensity shows depolarization toward the peak of Stokes I emission. This diminishing polarized flux implies that the alignment efficiency of the core dust grains is low within higher column densities where grain properties are likely different. The derived magnetic field geometry exhibits pinched field lines which are typical in evolved supercritical clouds where the magnetic field no longer support the core from collapsing. As a consequence for protostars, the gravitational pulling along the disk's long axis makes an equatorial bend to the field lines that, in turn, results in a hourglass shape. The SMA field structure agrees perfectly with the BIMA map. However, models are still necessary to provide a complete description of the evolutionary scenario of FIR 5.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2009

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