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 and 0.025 pc\,km\,s−1 based on 13CO images, and between 0.0025 and 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∝R1.58±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.
@article{arxiv.2006.04309,
title = {Rotation of Two Micron All Sky Survey Clumps in Molecular Clouds},
author = {Xuefang Xu and Di Li and Y. Sophia Dai and Paul F. Goldsmith and Gary A. Fuller},
journal= {arXiv preprint arXiv:2006.04309},
year = {2020}
}