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N. Hearn, G. Lake (Washington State Univ.), S. Lamb (Univ. of Illinois)
Collisions and mergers between massive galaxies can produce tidal tails and bridges that span several galactic radii in length. Observations of a number of such systems have revealed the presence of {\sc Hii} regions, {\rm H}\alpha emission, and molecular gas concentrations at the extremities of the tidal features despite their 108 -- 109 year dynamical timescales. Typically, prodigious star formation in colliding galaxies occurs within large-scale density enhancements in the ISM that develop throughout the disks over a period of 108 years. However, the molecular gas and ionized regions in the tidal structures provide evidence that enhanced star formation is taking place in lower-density regions long after the initial collision.
We present a set of galaxy collision models that have been generated by the n-body SPH code {\sc Tillamook}, focusing on the dynamics of material in the tidal structures. The effects of shock waves and radiative cooling in these regions is studied, and the kinematics of the tidal material are compared with velocity observations. Such investigations could have implications for our understanding of the efficiency of star formation in these limits.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.