Astron. Astrophys. Suppl. Ser. 142, 165-179
SPH simulations of clumps formation by dissipative collision of molecular clouds
I. Non magnetic case
E.P. Marinho1 - J.R.D. Lépine2
Send offprint request: E.P. Marinho,
1 - Instituto de Geociências e Ciências Exatas, Departamento de
Estatística, Matemática Aplicada e Computacional, UNESP,
Rua 10, 2527, 13500-230, Rio Claro SP, Brazil
Instituto Astronômico e Geofiisico,
Departamento de Astronomia, USP,
Av. Miguel Stefano, 4200, 04301-904 São Paulo SP, Brazil
Received September 7; accepted December 17, 1999
Copyright The European Southern Observatory (ESO)
Computer experiments of interstellar cloud collisions were performed with a new
smoothed-particle-hydrodynamics (SPH) code.
The SPH quantities were calculated
by using spatially adaptive smoothing lengths and the SPH fluid equations of
motion were solved by means of a hierarchical multiple time-scale leapfrog.
Such a combination of methods allows the code to deal with a large range of
A careful treatment of gas cooling by H, H2
, as well as a heating mechanism by cosmic rays and by H2
production on grains surface, were also included in the code.
The gas model
reproduces approximately the typical environment of dark molecular clouds.
The experiments were performed by impinging
two dynamically identical spherical clouds onto each other with
a relative velocity of 10 km s-1
but with a different impact
parameter for each case.
Each object has an initial density profile obeying an
-law with a cutoff radius of 10 pc and with an initial temperature of
As a main result, cloud-cloud collision triggers fragmentation
but in expense of a large
amount of energy dissipated, which occurred in the head-on case only.
Off-center collision did not allow remnants to fragment along the considered
However, it dissipated a
considerable amount of orbital energy.
Structures as small as 0.1 pc, with densities of
were observed in the more energetic collision.
Key words: hydrodynamics --
shock waves -- methods: numerical --
ISM: clouds --
ISM: kinematics and dynamics --