Issue |
Astron. Astrophys. Suppl. Ser.
Volume 142, Number 1, February II 2000
|
|
---|---|---|
Page(s) | 165 - 179 | |
DOI | https://doi.org/10.1051/aas:2000327 | |
Published online | 15 February 2000 |
SPH simulations of clumps formation by dissipative collision of molecular clouds
I. Non magnetic case
1
Instituto de Geociências e Ciências Exatas, Departamento de Estatística, Matemática Aplicada e Computacional, UNESP, Rua 10, 2527, 13500-230, Rio Claro SP, Brazil
2
Instituto Astronômico e Geofıisico, Departamento de Astronomia, USP, Av. Miguel Stefano, 4200, 04301-904 São Paulo SP, Brazil
Send offprint request to: E.P. Marinho
Received:
7
September
1999
Accepted:
17
December
1999
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
hydrodynamic quantities.
A careful treatment of gas cooling by H, H2, CO
and HII, 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
r-1-law with a cutoff radius of 10 pc and with an initial temperature of
20 K.
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
time ( Myr).
However, it dissipated a
considerable amount of orbital energy.
Structures as small as 0.1 pc, with densities of
cm-3,
were observed in the more energetic collision.
Key words: hydrodynamics / shock waves / methods: numerical / ISM: clouds / ISM: kinematics and dynamics / ISM: molecules
© European Southern Observatory (ESO), 2000