Abstract
Abstract We have obtained sensitive dust continuum polarization observations at 850 μm in the B213 region of Taurus using POL-2 on SCUBA-2 at the James Clerk Maxwell Telescope as part of the B-fields in STar-forming Region Observations (BISTRO) survey. These observations allow us to probe magnetic field (B-field) at high spatial resolution (∼2000 au or ∼0.01 pc at 140 pc) in two protostellar cores (K04166 and K04169) and one prestellar core (Miz-8b) that lie within the B213 filament. Using the Davis–Chandrasekhar–Fermi method, we estimate the B-field strengths in K04166, K04169, and Miz-8b to be 38 ± 14, 44 ± 16, and 12 ± 5 μG, respectively. These cores show distinct mean B-field orientations. The B-field in K04166 is well ordered and aligned parallel to the orientations of the core minor axis, outflows, core rotation axis, and large-scale uniform B-field, in accordance with magnetically regulated star formation via ambipolar diffusion taking place in K04166. The B-field in K04169 is found to be ordered but oriented nearly perpendicular to the core minor axis and large-scale B-field and not well correlated with other axes. In contrast, Miz-8b exhibits a disordered B-field that shows no preferred alignment with the core minor axis or large-scale field. We found that only one core, K04166, retains a memory of the large-scale uniform B-field. The other two cores, K04169 and Miz-8b, are decoupled from the large-scale field. Such a complex B-field configuration could be caused by gas inflow onto the filament, even in the presence of a substantial magnetic flux.
Highlights
According to the filamentary paradigm of star formation, lowmass stars predominantly form in dense cores that are distributed in a chain-like fashion along gravitationally unstable filamentary clouds (Hartmann 2002; André et al 2014; Tafalla & Hacar 2015; Marsh et al 2016)
Our analysis indicates that there is an equipartition among magnetic, turbulent, and gravitational energies in the core envelopes of K04166 and K04169
This strong geometrical correspondence suggests that the B-field, which is inherited from the large-scale uniform B-field, has played a significant role in core evolution by allowing gas contraction along field lines to form the core, subsequently governing its collapse via ambipolar diffusion, and collimating the outflows
Summary
According to the filamentary paradigm of star formation, lowmass stars predominantly form in dense cores that are distributed in a chain-like fashion along gravitationally unstable filamentary clouds (Hartmann 2002; André et al 2014; Tafalla & Hacar 2015; Marsh et al 2016). Studies of the B-field on cloud scales with Planck 850 μm lowresolution (∼5′ or ∼0.2 at 140 pc) polarization observations and optical and near-infrared (NIR) polarimetry of background stars have revealed that low-density gas striations are mostly aligned with the B-field, and high-density filamentary structures are oriented perpendicular to the B-field (Alves et al 2008; Sugitani et al 2010; Chapman et al 2011; Planck Collaboration et al.2016a; Wang et al 2020) These observations imply that material can accumulate along field lines and aid in the assembly of dense structures perpendicular to the B-field as a result of gravitational collapse and/or converging flows (see Ballesteros-Paredes et al.1999a; Hartmann et al 2001; Soler & Hennebelle 2017).
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