Droplets II: Internal Velocity Structures and Potential Rotational Motions in Coherent Cores. (arXiv:1908.04367v1 [astro-ph.GA])

Droplets II: Internal Velocity Structures and Potential Rotational Motions in Coherent Cores. (arXiv:1908.04367v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Chen_H/0/1/0/all/0/1">Hope How-Huan Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pineda_J/0/1/0/all/0/1">Jaime E. Pineda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Offner_S/0/1/0/all/0/1">Stella S. R. Offner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goodman_A/0/1/0/all/0/1">Alyssa A. Goodman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burkert_A/0/1/0/all/0/1">Andreas Burkert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Friesen_R/0/1/0/all/0/1">Rachel K. Friesen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rosolowsky_E/0/1/0/all/0/1">Erik Rosolowsky</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scibelli_S/0/1/0/all/0/1">Samantha Scibelli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shirley_Y/0/1/0/all/0/1">Yancy Shirley</a>

We present an analysis of the internal velocity structures of the newly
identified sub-0.1 pc coherent structures, droplets, in L1688 and B18. By
fitting 2D linear velocity fields to the observed maps of velocity centroids,
we determine the magnitudes of linear velocity gradients and examine the
potential rotational motions that could lead to the observed velocity
gradients. The results show that the droplets follow the same power-law
relation between the velocity gradient and size found for larger-scale dense
cores. Assuming that rotational motion giving rise to the observed velocity
gradient in each core is a solid-body rotation of a rotating body with a
uniform density, we derive the “net rotational motions” of the droplets. We
find a ratio between rotational and gravitational energies, $beta$, of $sim
0.046$ for the droplets, and when including both droplets and larger-scale
dense cores, we find $beta sim 0.039$. We then examine the alignment between
the velocity gradient and the major axis of each droplet, using methods adapted
from the histogram of relative orientations (HRO) introduced by Soler et al.
(2013). We find no definitive correlation between the directions of velocity
gradients and the elongations of the cores. Lastly, we discuss physical
processes other than rotation that may give rise to the observed velocity
field.

We present an analysis of the internal velocity structures of the newly
identified sub-0.1 pc coherent structures, droplets, in L1688 and B18. By
fitting 2D linear velocity fields to the observed maps of velocity centroids,
we determine the magnitudes of linear velocity gradients and examine the
potential rotational motions that could lead to the observed velocity
gradients. The results show that the droplets follow the same power-law
relation between the velocity gradient and size found for larger-scale dense
cores. Assuming that rotational motion giving rise to the observed velocity
gradient in each core is a solid-body rotation of a rotating body with a
uniform density, we derive the “net rotational motions” of the droplets. We
find a ratio between rotational and gravitational energies, $beta$, of $sim
0.046$ for the droplets, and when including both droplets and larger-scale
dense cores, we find $beta sim 0.039$. We then examine the alignment between
the velocity gradient and the major axis of each droplet, using methods adapted
from the histogram of relative orientations (HRO) introduced by Soler et al.
(2013). We find no definitive correlation between the directions of velocity
gradients and the elongations of the cores. Lastly, we discuss physical
processes other than rotation that may give rise to the observed velocity
field.

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