The Milky Way atlas for linear filaments II. clump rotation versus filament orientation

TL;DR

This study investigates the kinematic properties of dense clumps along filaments in the Milky Way, revealing that clump rotation is generally insignificant for support against collapse and shows no preferred alignment with filament orientation.

Contribution

It provides the first detailed analysis of the relationship between clump rotation and filament orientation, using a large dataset from the Milky Way atlas and SEDIGISM survey.

Findings

Clump specific angular momentum increases with size following a power-law.

Clump rotational support against gravity is negligible.

No correlation between clump rotation axes and filament orientation.

Abstract

Dense clumps distributed along filaments are the immediate medium for star formation. Kinematic properties of the clumps, such as velocity gradient and angular momentum, combined with filament orientation, provide important clues to the formation mechanism of filament-clump configurations and the role of filaments in star formation. By cross-matching the Milky Way atlas for linear filaments and the Structure, Excitation and Dynamics of the Inner Galactic Interstellar Medium (SEDIGISM) 13CO (2-1) data, we aim to derive the velocity gradient and its direction, the specific angular momentum (J/M), and the ratio (\beta) between the rotational energy and gravitational energy of clumps, as well as to investigate the alignment between clump rotation and filament orientation. We found a monotonic increase in J/M as a function of clump size (R), following a power-law relation J/M~\propto~R^{1.5\pm0.2}. The ratio \beta ranges from 1.1~\times~10^{-5} to 0.1, with a median value 1.0~\times~10^{-3}, suggesting that clump rotation provides insignificant support against gravitational collapse. The distribution of the angle between clump rotation and natal filament orientation is random, indicating that the clumps' rotational axes have no discernible correlation with the orientation of their hosting filaments. Counting only the most massive clump in each filament also finds no alignment between clump rotation and filament orientation.