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N. C. Hearn (Center for Theoretical Astrophysics, Department of Physics, University of Illinois), S. A. Lamb (Center for Theoretical Astrophysics, Department of Physics and Department of Astronomy, University of Illinois), P. Anninos, G. Bazan, S. D. Murray, J. M. Owen (Lawrence Livermore National Laboratory)
Arp 220 is an ongoing merger between two gas-rich galaxies exhibiting massive star formation, as well as galactic-scale lobe- and plume-like structures in the interstellar medium and in the stellar distribution. Chandra X-Ray Telescope observations show that this system, like a number of colliding or merging galaxies, possesses a halo of hot (~107 K) gas extending beyond the visible components of Arp 220; this halo is concentrated into two lobe-like regions, which appear to emanate from the central region of this system and span roughly 25 kpc from end to end. Using a new n-body and SPH simulation code that includes heat input from shock waves and a realistic, chemical species-dependent, radiative cooling model, the contribution of the colliding gaseous disks and the gravitational contraction of the galactic components to the production of hot halo gas is explored. We show that the collision of two equal-mass, gas-rich disk galaxies can produce many of the morphological structures seen in Arp 220, and that shock waves in the interstellar medium can produce gas with temperatures comparable to those of the hot halo of Arp 220. The plume-like structures of hot gas that extend about 5.5 kpc on either side of the nuclear region also have analogues within this simulation. However, it appears likely that these features are due to a superwind from a central, massive starburst, as previously suggested. We acknowledge support from DOE contract LLNL B506657 and NASA award GO0-1166B to the University of Illinois.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.