Near-IR imaging polarimetry toward a bright-rimmed cloud: Magnetic field in SFO 74

Kusune, T. and Sugitani, K. and Miao, Jingqi and Tamura, M. and Sato, Y. and Kwon, J. and Watanabe, M. and Nishiyama, S. and Nagayama, T. and Sato, S. (2014) Near-IR imaging polarimetry toward a bright-rimmed cloud: Magnetic field in SFO 74. Astrophysical Journal, 798 (1). pp. 60-76. ISSN 0004-637X. (doi:https://doi.org/10.1088/0004-637X/798/1/60) (Full text available)

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Abstract

We have made near-infrared (JHKs) imaging polarimetry of a bright-rimmed cloud (SFO 74). The polarization vector maps clearly show that the magnetic field in the layer just behind the bright rim is running along the rim, quite different from its ambient magnetic field. The direction of the magnetic field just behind the tip rim is almost perpendicular to that of the incident UV radiation, and the magnetic field configuration appears to be symmetric as a whole with respect to the cloud symmetry axis. We estimated the column and number densities in the two regions (just inside and far inside the tip rim) and then derived the magnetic field strength, applying the Chandrasekhar-Fermi method. The estimated magnetic field strength just inside the tip rim, ~90 μG, is stronger than that far inside, ~30 μG. This suggests that the magnetic field strength just inside the tip rim is enhanced by the UV-radiation-induced shock. The shock increases the density within the top layer around the tip and thus increases the strength of the magnetic field. The magnetic pressure seems to be comparable to the turbulent one just inside the tip rim, implying a significant contribution of the magnetic field to the total internal pressure. The mass-to-flux ratio was estimated to be close to the critical value just inside the tip rim. We speculate that the flat-topped bright rim of SFO 74 could be formed by the magnetic field effect.

Item Type: Article
Additional information: (c) �2015. The American Astronomical Society. All rights reserved.
Uncontrolled keywords: Infrared: Stars, ISM: Individual objects (SFO 74), ISM: Magnetic fields, ISM: Structure, Polarization
Subjects: Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: Giles Tarver
Date Deposited: 04 Aug 2015 14:24 UTC
Last Modified: 13 Jan 2017 16:18 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/50013 (The current URI for this page, for reference purposes)
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