- Gravitational Fragmentation: A Comparison with W49A
The process of gravitational fragmentation of molecular clouds is investigated through a
comparison of numerical and observational results. The expected millimeter wave molecular
line emission from a model fragmenting cloud generated by a numerical hydrodynamic simulation
is calculated and compared with observations of HCO+ from the star-forming region W49A.
This investigation suggests that the rotating ring of H II regions, the necklace in W49A,
may have formed in the gravitational fragmentation of a flattened rotating molecular cloud.
Eric R. Keto, John C. Lattanzio & Joe J. Monaghan, 1991, ApJ, 383, 639
- Collisions Between High Latitude Clouds
A three-dimensional model for hydrodynamic and radiative transfer simulations of
collisions between high-latitude clouds is described. The smooth particle hydrodynamics
code by Lattanzio and Henriksen (1988) is used to compute the velocity and density fields
in the impacted clouds along with a recently developed radiative transfer code to compute
C13O line radiation from the simulated source. The model shows the following: the so
far unexplained energy source for the broad CO line wings reported by
Blitz, Magnani, and Wandel (1987) derives from the collisions; collisions can induce
rapid gravitational collapse and star formation in these clouds which are otherwise supported
against gravitational contraction via their internal energy content; and the external
pressure due to intercloud H I, first proposed by Keto and Myers (1986), plays a
significant role in the stability and evolution of the high-latitude clouds.
Eric R. Keto & John C. Lattanzio, 1989, ApJ, 346, 184