SIMBAD references

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/m2 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.