Lattanzio, John C. | Search NASA

NASA NTRS1991

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.

Keto, Eric R.↗

NASA NTRS1991

A simulation of the collapse and fragmentation of cooling molecular clouds

The application of the Smoothed Particle Hydrodynamics method to the fragmentation of rotating cloud and disk systems is described, allowing for molecular cooling due to H2 and CO. A novel approach to solving Poisson's equation for disklike structures which exploits the multigrid algorithm is also described. Numerical studies are presented which investigate the evolution of both rotating clouds and Maclaurin disks, in each case with both an isothermal equation of state and with molecular cooling. The results establish the influence of molecular cooling on the fragmentation of molecular clouds. The isothermal sequences, if they fragment at all, do so into far fewer lumps than the cooling sequences. This is not due to a cooling instability as such, but rather to the reduced thermal support. One of the sequences shows a remarkable similarity to the W49A star-forming region.

Monaghan, Joe J.↗