Magnetic fields and outflows in the large Bok globule CB 54

Abstract

We have observed the large Bok globule CB 54 in 850𝜇m polarised light using the POL-2 polarimeter on the James Clerk Maxwell Telescope (JCMT). We find that the magnetic field in the periphery of the globule shows significant, ordered deviation from the mean field direction in the globule centre. This deviation appears to correspond with the extended but relatively weak 12 CO outflow emanating from the Class 0 sources at the centre of the globule. Energetics analysis suggests that if the outflow is reshaping the magnetic field in the globule's periphery, then we can place an upper limit of < 27 𝜇G on the magnetic field strength in the globule's periphery. Comparison with archival Planck and CARMA measurements shows that the field in the centre of the globule is consistent over several orders of magnitude in size scale, and oriented parallel to the density structure in the region in projection. We thus hypothesise that while non-thermal motions in the region may be sub-Alfvénic, the magnetic field is subdominant to gravity over a wide range of size scales. Our results suggest that even a relatively weak outflow may be able to significantly reshape magnetic fields in star-forming regions on scales > 0.1 pc.

First BISTRO observations of the dark cloud Taurus L1495A-B10: the role of the magnetic field in the earliest stages of low-mass star formation

“…More generally, YSO outflows appear to have the potential to reshape magnetic fields in their vicinities (e.g. Yen et al 2021;Lyo et al 2021;Pattle et al 2022b), suggesting that we cannot infer the magnetic initial conditions for star formation in environments with embedded YSOs.…”