Comparison of Prestellar Core Elongations and Large-Scale Molecular Cloud Structures in the Lupus I Region

TL;DR

This study analyzes the shapes and orientations of prestellar cores in the Lupus I cloud, finding no correlation with large-scale filament structures or magnetic fields, suggesting local dynamics influence core morphology.

Contribution

It provides the first statistical comparison of core elongations with large-scale filament and magnetic field orientations in Lupus I, highlighting local effects over large-scale influences.

Findings

Core elongations are randomly oriented with respect to large-scale filament shape.

No correlation between core morphology and large-scale magnetic field orientation.

Local filament dynamics and small-scale magnetic variations likely influence core orientations.

Abstract

Turbulence and magnetic fields are expected to be important for regulating molecular cloud formation and evolution. However, their effects on subparsec to 100 parsec scales, leading to the formation of starless cores, is not well understood. We investigate the prestellar core structure morphologies obtained from analysis of the Herschel-SPIRE 350 $\mu$m maps of the Lupus I cloud. This distribution is first compared on a statistical basis to the large scale shape of the main filament. We find the distribution of the elongation position angle of the cores to be consistent with a random distribution, which means no specific orientation of the morphology of the cores is observed with respect to a large-scale filament shape model for Lupus I, or relative to a large-scale bent filament model. This distribution is also compared to the mean orientation of the large-scale magnetic fields probed at 350 $\mu$m with the Balloon-borne Large Aperture Telescope for Polarimetry (BLASTPol) during its 2010 campaign. Here again we do not find any correlation between the core morphology distribution and the average orientation of the magnetic fields on parsec scales. Our main conclusion is that the local filament dynamics - including secondary filaments that often run orthogonally to the primary filament - and possibly small-scale variations in the local magnetic field direction, could be the dominant factors for explaining the final orientation of each core.