Astrophysics and Space Science vol:348 issue:2 pages:327-335
An attempt is made here to revisit structure formation
in a proto-stellar cloud during the early phase of evolution.
A molecular cloud subject to a set of various initial
conditions in terms of initial temperature and amplitude of
azimuthal density perturbation is investigated numerically.
Special emphasis is on the analysis of ring- and spiral-type
instabilities that have shown dependence on certain initial
conditions chosen for a rotating solar mass cloud of molecular
hydrogen. Generally, a star-forming hydrogen gas is considered
to be initially at 10 K.We have found that a possible
oscillation around this typical value can affect the fate of a
collapsing cloud in terms of its evolving structural properties
leading to proto-star formation. We explored the initial temperature
range of the cloud between 8 K to 12 K and compared
the physical properties of each within the first phase
of proto-star formation. We suggest that the spiral structures
are more likely to form in strongly perturbed molecular
cores that initiate their phase of collapse from temperatures
below 10 K, whereas cores with initial temperatures above
10 K develop, instead of a spiral structure, a ring-type structure
which subsequently experiences fragmentation. A transition
from a spiral to ring instability can be observed at a
typical initial temperature of 10 K.