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Session 109 - Galaxies: Collisions, Counter-Rotating Disks.
Display session, Thursday, January 18
North Banquet Hall, Convention Center

[109.03] Where Galaxies Collide: Numerical Simulation of the M81 System

P. S. Li, H. A. Thronson (U of Wyo)

We used advanced numerical techniques to simulate the interaction between the three major galaxies in the M81 system, taking into account gravitational and hydrodynamics effects, star formation, supernova explosions, and the heating/cooling of the ISM by using a modified TREESPH code. Extensive HI observations are used to contrain the models, which are required to produce `concentrations' and `bridges' seen in the atomic gas. In our model, M81 and M82 are both 4-component disk galaxies, including gas disks. NGC3077 is a spherical Jaffe model without gas. Different orbital inclinations of NGC3077 are tried in our simulations. The results show that the orbital inclination of NGC3077 of 15-30\deg, which was believed to be about 45\deg relative to the M81 galactic plane, reproduces the best HI gas distribution as observed. Massive star formation happens in M82 during the close encounter as the result of tidal pertubation. After perigal, the star formation rate keeps increasing because of the infall of gas. NGC3077 changes to an elliptical shape as the result of tidal effects, with an orientation similar to observations. The model system is presented by using BIG (Brightness Image of Galaxy), which is designed to calculate the relative bolometric brightness images of galaxies according to the masses and ages of the stellar particles in the model system. This work was supported by the Pittsburgh Supercomputing Center.

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