2020ApJ...898..122X

We have analyzed the rotational properties of 12 clumps using ¹³CO (1-0) and C¹⁸O (1-0) maps of the Five College Radio Astronomy Observatory 13.7 m radio telescope. The clumps, located within molecular clouds, have radii (R) in the range of 0.06-0.27 pc. The direction of clump elongation is not correlated with the direction of the velocity gradient. We measured the specific angular momentum (J/M) to be between 0.0022-0.025 pc km s^–1 based on ¹³CO images, and between 0.0025-0.021 pc km s^–1 based on C¹⁸O images. The consistency of J/M based on different tracers indicates the ¹³CO and C¹⁸O in dense clumps trace essentially the same material despite significantly different opacities. We also found that J/M increases monotonically as a function of R in power-law form, J/M∝R^1.58±0.11^. The ratio between rotation energy and gravitational energy, β, ranges from 0.0012 to 0.018. The small values of β imply that rotation alone is not sufficient to support the clump against gravitational collapse.