Abstract:
LDN 328 is cited as an example of a fairly isolated clump contracting to form multiple sub-cores, possibly through
gravitational fragmentation. In one of these sub-cores, a proto-brown dwarf (L328-IRS) candidate is in the process
of formation through the self-gravitating contraction, similar to the formation scenario of a low-mass star. We
present results of our optical and near-infrared polarization observations of regions toward LDN 328. This is the
first observational attempt to map the magnetic field geometry of a cloud harboring a proto-brown dwarf candidate
associated with a sub-parsec-scale molecular outflow. On a parsec scale, the magnetic field is found to follow the
curved structure of the cloud showing a head–tail morphology. The magnetic field is found to be well ordered over
a 0.02–0.2 pc scale around L328-IRS. Taking into account the uncertainties in the determination of position angles,
the projected angular offset between the magnetic field direction and the outflow axis is found to be in the range of
0°–70°. Considering outflow to be the proxy for the rotation axis, the result obtained in this study implies that the
rotation axis in L328 is preferably parallel to the local magnetic field. The magnetic field strength estimated in the
close vicinity of L328-IRS is ∼20 μG. Results from the present study suggest that the magnetic field may be
playing a vital role even in the cores that are forming sub-stellar sources.
