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

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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) $^{13}$CO (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 $J/M~\propto ~R^{1.5\pm 0.2}$. 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.