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The magnetic field of the H ii region NGC 6334A from Faraday rotation

Authors

  • L. F. Rodríguez,

    Corresponding author
    1. Centro de Radiostronomía y Astrofísica, Universidad Nacional Autónoma de México, Apdo. Postal 3-72, Morelia, Michoacán 58089, México
    2. Astronomy Department, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah 21589, Saudi Arabia
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  • Y. Gómez,

    1. Centro de Radiostronomía y Astrofísica, Universidad Nacional Autónoma de México, Apdo. Postal 3-72, Morelia, Michoacán 58089, México
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  • D. Tafoya

    1. Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan
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E-mail: l.rodriguez@crya.unam.mx

ABSTRACT

We have studied the polarization characteristics and Faraday rotation of the extragalactic radio source J17204−3554, which appears projected on the north lobe of the Galactic H ii region NGC 6334A. From observations made with the Very Large Array at 6.0 and 3.6 cm in three different epochs (1994, 1997 and 2006), we estimate a rotation measure of +5100 ± 900 rad m−2 for the extragalactic source. This large rotation measure implies a line-of-sight average magnetic field of B≃+ 36 ± 6 μG, the largest obtained by this method for an H ii region. NGC 6334A is significantly denser than other H ii regions studied and this larger magnetic field is expected on the grounds of magnetic flux conservation. The ratio of thermal to magnetic pressure is ∼5 in the range of values determined for more diffuse H ii regions.

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