BIMA N2H+ 1-0 mapping observations of L183 -- fragmentation and spin-up in a collapsing, magnetized, rotating, pre-stellar core

TL;DR

This study uses BIMA observations to reveal the internal substructure, fragmentation, and spin-up dynamics of the pre-stellar core L183, highlighting its rotation aligned with magnetic fields and potential to form multiple stars.

Contribution

First detailed mapping of L183's substructure showing fragmentation and spin-up consistent with angular momentum conservation during collapse.

Findings

Identified three distinct clumps within L183.

Detected strong velocity gradients indicating rotation and spin-up.

Found the core's rotation axis aligned with magnetic field direction.

Abstract

We have used the Berkeley-Illinois-Maryland Array (BIMA) to make deep N2H+ 1-0 maps of the pre-stellar core L183, in order to study the spatial and kinematic substructure within the densest part of the core. Three spatially and kinematically distinct clumps are detected, which we label L183-N1, L183-N2 and L183-N3. L183-N2 is approximately coincident with the submillimetre dust peak and lies at the systemic velocity of L183. Thus we conclude that L183-N2 is the central dense core of L183. L183-N1 and 3 are newly-discovered fragments of L183, which are marked by velocity gradients that are parallel to, but far stronger than, the velocity gradient of L183 as a whole, as detected in previous single-dish data. Furthermore, the ratio of the large-scale and small-scale velocity gradients, and the ratio of their respective size-scales, are consistent with the conservation of angular momentum for a rotating, collapsing core undergoing spin-up. The inferred axis of rotation is parallel to the magnetic field direction, which is offset from its long axis, as we have seen in other pre-stellar cores. Therefore, we propose that we have detected a fragmenting, collapsing, filamentary, pre-stellar core, rotating about its B-field, which is spinning up as it collapses. It will presumably go on to form a multiple protostellar system.