A First Look at the BISTRO Observations of the Rho OPH-A Core

We present 850 μm imaging polarimetrydata of the ρ Oph-A core taken with the Submillimeter Common-User BolometerArray-2 (SCUBA-2) and its polarimeter(POL-2), as part of our ongoing survey project, BISTRO (Bfields In STar forming RegiOns). The polarization vectors are used to identify the orientation of the magnetic field projected on the plane of the sky at a resolution of 0.01 pc. We identify 10 subregions with distinct polarization fractions and angles in the 0.2 pc ρ Oph A core; some of them can be part of a coherent magnetic field structure in the ρ Oph region. The results are consistent with previous observations of the brightest regions of ρ Oph-A, where the degreesof polarizationare at a level of a few percents, but our data reveal for the first time the magnetic field structures in the fainter regions surrounding the core where the degreeof polarizationis much higher (> 5%). A comparison with previous near-infrared polarimetric data shows that there are several magnetic field components which are consistent at near-infrared and submillimeter wavelengths. Using the Davis-Chandrasekhar-Fermi method, we also derive magnetic field strengths in several sub-core regions, which range from approximately 0.2 to 5 mG.We also find a correlation between the magnetic field orientations projected on the sky with the core centroid velocity components.