Simulations of Colliding Uniform Density H2 Clouds


In this paper we present a set of numerical simulations designed to study the interaction process of HII molecular clouds. For the initial conditions we assume head-on and oblique collisions of binary identical clouds placedadjacent to one another, with their surfaces just in contact. The colliding initial clouds are uniform density molecular gas spheres with rigid body rotation. The cloud initial conditions are chosen to favor its gravitational collapse as an isolated system. To study the effect of the self-gravity of the cloud in the collision process, we consider several models in which the approaching speed of the colliding clouds increases from zero up to several times the initial sound speed of the barotropic gas. We present the outcome of these collision models for several values of the impact parameter b, which depends on the initial radius of the cloud. We have explored the parameter space of the approaching velocity Vapp of the colliding clouds for configurations that may result in seeds for the formation of more complex systems. Such systems are expected to include filaments and gas clumps, where the star formation process is still possible despite the occurrence of the collision. We show hereby that collisions may have a major and favorable influence on the star formation process.

Share and Cite:

Arreaga-García, G. , Klapp, J. and Morales, J. (2014) Simulations of Colliding Uniform Density H2 Clouds. International Journal of Astronomy and Astrophysics, 4, 192-220. doi: 10.4236/ijaa.2014.41018.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] Scoville, N.Z., Sanders, D.B. and Clemens, D.P. (1986) High-Mass Star Formation Due to Cloud-Cloud Collisions. Astrophysical Journal, 310, L77-L81.
[2] Wang, J.J., Chen, W.P., Miller, M., Qin, S.L. and Wu, Y.F. (2004) Massive Star Formation Triggered by Collision between Galactic and Accreted Intergalactic Clouds. Astrophysical Journal, 614, L105-L108.
[3] Burkert, A. and Alves, J. (2009) The Inevitable Future of the Starless Core Barnard 68. Astrophysical Journal, 695, 1308-1314.
[4] Anathpindika, S. (2009) Supersonic Cloud Collision. I. Astronomy and Astrophysics, 504, 437-460.
[5] Hausman, M.A. and Ostriker, J.P. (1978) Galactic Cannibalism. III—The Morphological Evolution of Galaxies and Clusters. Astrophysical Journal, 224, 320-336.
[6] Lattanzio, J.C., Monaghan, J.J., Pongracic, H. and Schwarz, M.P. (1985) Interstellar Cloud Collisions. Monthly Notices of the Royal Astronomical Society, 215, 125-147.
[7] Kimura, T. and Tosa, M. (1996) Collision of Clumpy Molecular Clouds. Astronomy and Astrophysics, 308, 979-987.
[8] Klein, R.I. and Woods, D.T. (1998) Bending Mode Instabilities and Fragmentation in Interstellar Cloud Collisions: A Mechanism for Complex Structure. Astrophysical Journal, 497, 777-799.
[9] Marinho, E.P. and Lepine, J.R.D. (2000) SPH Simulations of Clumps Formation by Dissipative Collision of Molecular Clouds. I. Non Magnetic Case. Astronomy and Astrophysics. Supplement Series, 142, 165-179.
[10] Smith, J. (1980) Cloud-Cloud Collisions in the Interstellar Medium. Astrophysical Journal, 238, 842-852.
[11] Kitsionas, S. and Whitworth, A.P. (2007) High-Resolution Simulations of Clump-Clump Collisions Using SPH with Particle Splitting. Monthly Notices of the Royal Astronomical Society, 378, 507-524.
[12] Anathpindika, S. (2010) Collision between Dissimilar Clouds: Stability of the Bow-Shock and the Formation of PreStellar Cores. Monthly Notices of the Royal Astronomical Society, 405, 1431-1443.
[13] Whithworth, A.P. and Pongracic, H. (1991) Cloud-Cloud Collisions and Fragments. In: Falgarone, E., Boulangeer, F. and Duvert, G., Eds., Fragmentation of Molecular Clouds and Star Formation, International Astronomical Union, Kluwer Academic Publishers, Berlin, 523-525.
[14] Bergin, E. and Tafalla, M. (2007) Cold Dark Clouds: The Initial Conditions for Star Formation. Annual Review of Astronomy and Astrophysics, 45, 339-396. 071206.100404
[15] Myers, P.C. and Benson, P.J. (1983) Dense Cores in Dark Clouds. II-NH3 Observations and Star Formation. Astrophysical Journal, 266, 309-320.
[16] Plummer, H.C. (1911) On the Problem of Distribution in Globular Star Clusters. Monthly Notices of the Royal Astronomical Society, 71, 460-470.
[17] Whithworth, A.P. and Ward-Thompson, D. (2001) An Empirical Model for Protostellar Collapse. Astrophysical Journal, 547, 317-322.
[18] Myers, P.C. (2005) Centrally Condensed Collapse of Starless Cores. Astrophysical Journal, 623, 280-290.
[19] Arreaga, G. and Klapp, J. (2010) The Gravitational Collapse of Plummer Protostellar Clouds. Astronomy and Astrophysics, 509, A96-A111.
[20] Bodenheimer, P., Burkert, A., Klein, R.I. and Boss, A.P. (2000) Multiple Fragmentation of Protostars. In: Mannings, V.G., Boss, A.P. and Russell, S.S., Eds., Protostars and Planets IV, University of Arizona Press, Tucson, 675-701.
[21] Sigalotti, L.G. and Klapp, J. (2001) Gravitational Collapse and Fragmentation of Molecular Cloud Cores. International Journal of Modern Physics D, 10, 115-211. 18271801000706
[22] Boss, A.P., Fisher, R.T., Klein, R. and McKee, C.F. (2000) The Jeans Condition and Collapsing Molecular Cloud Cores: Filaments or Binaries? Astrophysical Journal, 528, 325-335. 308160
[23] Arreaga, G., Klapp, J., Sigalotti, L.G. and Gabbasov, R. (2007) Gravitational Collapse and Fragmentation of Molecular Cloud Cores with GADGET-2. Astrophysical Journal, 666, 290-308.
[24] Arreaga, G., Saucedo, J., Duarte, R. and Carmona, J. (2008) Hydrodynamical Simulations of the Non-Ideal Gravitational Collapse of a Molecular Gas Cloud. Revista Mexicana de Astronomía y Astrofísica, 44, 259-284.
[25] Whitehouse, S.C. and Bate, M.R. (2006) The Thermodynamics of Collapsing Molecular Cloud Cores Using Smoothed Particle Hydrodynamics with Radiative Transfer. Monthly Notices of the Royal Astronomical Society, 367, 32-38.
[26] Spitzer, L. (1978) Physical Processes in the Interstellar Médium. Wiley, Hoboken.
[27] Bekki, K., Beasley, M., Forbes, D. and Couch, W.J. (2004) Formation of Star Clusters in the Large Magellanic Cloud and Small Magellanic Cloud. I. Preliminary Results on Cluster Formation from Colliding Gas Clouds. Astrophysical Journal, 602, 730-737.
[28] Larson, R. (1981) Turbulence and Star Formation in Molecular Clouds. Monthly Notices of the Royal Astronomical Society, 194, 809-826.
[29] Chapman, S., Pongraic, H., Disney, M., Nelson, A., Turner, J. and Whitworth, A. (1992) The Formation of Binary and Multiple Star Systems. Nature, 359, 207-210.
[30] Springel, V. (2005) The Cosmological Simulation Code GADGET-2. Monthly Notices of the Royal Astronomical Society, 364, 1105-1134.
[31] Gingold, R.A. and Monaghan, J.J. (1977) Smooth Particle Hydrodynamics: Theory and Applications to Non-Spherical Stars. Monthly Notices of the Royal Astronomical Society, 181, 375-389.
[32] Balsara, D. (1995) von Neumann Stability Analysis of Smooth Particle Hydrodynamics-Suggestions for Optimal Algorithms. Journal of Computational Physics, 121, 357-372. S0021-9991(95)90221-X
[33] Truelove, J.K., Klein, R.I., McKee, C.F., Holliman, J.H., Howell, L.H. and Greenough, J.A. (1997) The Jeans Condition: A New Constraint on Spatial Resolution in Simulations of Isothermal Self-gravitational Hydrodynamics. Astrophysical Journal, 489, L179-L183. 310975
[34] Bate, M.R. and Burkert, A. (1997) Resolution Requirements for Smoothed Particle Hydrodynamics Calculations with Self-Gravity. Monthly Notices of the Royal Astronomical Society, 288, 1060-1072.
[35] Sigalotti, L.G., Klapp, J., Sira, E., Melean, Y. and Hamsy, A. (2003) SPH Simulations of Time-Dependent Poiseuille Flow at Low Reynolds Numbers. Journal of Computational Physics, 191, 622-638.
[36] Sigalotti, L.G., Lopez, H., Donoso, A., Sira, E. and Klapp, J. (2006) A Shock-Capturing SPH Scheme Based on Adaptive Kernel Estimation. Journal of Computational Physics, 212, 124-149.
[37] Vishniac, E.T. (1983) The Dynamic and Gravitational Instabilities of Spherical Shocks. Astrophysical Journal, 274, 152-167.
[38] Vishniac, E.T. (1994) Nonlinear Instabilities in Shock-Bounded Slabs. Astrophysical Journal, 428, 186-208.
[39] Springel, V., Yoshida, N. and White, D.M. (2001) GADGET: A Code for Collisionless and Gasdynamical Cosmological Simulations. New Astronomy, 6, 79-117. 00042-2
[40] Larson, R. (1972) Infall of Matter in Galaxies. Nature, 236, 21-23. 236021a0
[41] Nelson, R.P. and Papaloizou, C.B. (1994) Variable Smoothing Lengths and Energy Conservation in Smoothed Particle Hydrodynamics. Monthly Notices of the Royal Astronomical Society, 270, 1-20.

Copyright © 2022 by authors and Scientific Research Publishing Inc.

Creative Commons License

This work and the related PDF file are licensed under a Creative Commons Attribution 4.0 International License.