Mapping the magnetic field in filamentary cloud L1495/B211 with SOFIA HAWC+

Long filaments of dense molecular gas are commonly found inside GMCs (e.g. Bergin & Tafalla 2007, André et al. 2014, André 2017), such as L1495/B211 in the Taurus region (e.g. Palmeirim et al. 2013). High resolution images of these filaments from the Herschel space telescope reveal complex filamentary substructures (e.g. André et al. 2014). Near infrared polarization observations by Chapman et al. (2011) at 200” resolution and recent Planck observations (Planck Collaboration Int. XXXV 2016) at 10’ resolution show that the large-scale low resolution external magnetic field is roughly perpendicular to the long axis of the B211 filaments. We have conducted high-resolution polarization mapping of the starless B211 region of the filamentary cloud L1495 using SOFIA HAWC+. The HAWC+ observation at 28.1” resolution reveals more complex magnetic field structures inside the cloud, as predicted in a numerical simulation by Li & Klein (2019). The dispersion of position angles of polarization vectors is about 44°. Using the Davis-Chandrasekhar-Fermi method, with the velocity data obtained from an IRAM 30m C18O (1-0) observation, the plane of sky magnetic field strength inside the cloud is estimated to be in the range 10 - 36 μG, depending on location. Velocity profiles also indicate multiple components at some locations in the region, as also seen in Hacar et al. (2013). The Alfven Mach number determined in most parts of the B211 region is ~1, indicating that magnetic field is dynamically important in this region. Two small regions appear more chaotic in the Herschel map, indicating highly turbulent states, which can be characterized by higher Alfven Mach numbers of 1.6 ~ 3.3. We shall use our high-resolution simulation of filamentary molecular cloud formation to explain the dynamical state of L1495.