Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravity as the main driver of non-thermal motions in massive star
  formation   The origin of non-thermal motions in massive star forming regions can be
ascribed to turbulence acting against the gravitational collapse, or to the
self-gravity itself driving the rapid global collapse. The dependence between
velocity dispersion, radius and clouds surface density found by Heyer et al.
(2009), $\sigma/R^{1/2}\propto \Sigma^{1/2}$, has been interpreted in terms of
global collapse of clouds. In this work we demonstrate that this relation is an
expression of a more general relation between accelerations. We introduce the
gravo-turbulent acceleration, a$_k$, which describe the non-thermal motions in
each region, and the acceleration generated by the gravitational field a$_G$,
which is proportional to $\Sigma$. We also introduce a new coefficient, the
force partition coefficient $\alpha_{for}$ which is equivalent to the virial
parameter but does not distinguish between collapsing and non-collapsing
regions. In this work we use the a$_k$ - a$_G$ formalism in the analysis of a
new sample of 16 massive starless clumps (MSCls) combined with data from the
literature. We show that a$_k$ and a$_G$ are not independent. The non-thermal
motions in each region can originate from both local turbulence and
self-gravity but overall the data in the a$_k$ vs. a$_G$ diagram demonstrate
that the majority of the non-thermal motions originate from self-gravity. We
further show that all the MSCls with $\Sigma\geq 0.1$ g cm$^{-2}$ show signs of
infall motions, a strong indication that the denser regions are the first to
collapse. Finally, we include in the formalism the contribution of an external
pressure and the magnetic fields.

30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
2
The categories of this paper are: math