2016MNRAS.462.2266S

We present a polarimetric study of the RCW121 star-forming region to derive the orientation of the sky-projected magnetic field component traced by the polarization vectors, the morphology of which tends to follow the cloud's structure. Individual polarization-angle values are consistent across the different bands, having a broad distribution towards the RCW121 H II region. We estimate the corresponding magnetic field orientation in the H II region to have a mean value of -12deg ± 7deg. RCW121 shows an elongated shape in the same direction as the magnetic field orientation, which may be evidence that magnetic pressure opposes the H II region expansion. Serkowski's relation was used to determine individual values of the total-to-selective extinction ratio (R_V) distribution and a weighted mean value of R_V = 3.17 ± 0.05. We derive a foreground component of the polarization degree that is consistent with the literature value for this Galactic region.