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Session 123 - Galaxy Evolution: Dwarfs & Clusters.
Oral session, Saturday, January 10

[123.04] Numerical Simulation of M81-M82-NGC3077 System Using a Parallelized TreeSPH code

P. S. Li (U. Wyoming, U. Illinois), H. A. Thronson Jr. (U. Wyoming, NASA HQ)

We used a parallelized TreeSPH code using Message Passing Interface (MPI) to simulate the interaction among the three major component galaxies in the M81 system, taking into account gravitational and hydrodynamical effects, star formation, supernova explosions, and the heating/cooling of the ISM. With the parallelized code, we are able to simulate this system with 400,000 particles, in which 150,000 are gas particles, with about a one billion year timescale. With this amount of gas particles, we can go down to the resolution of 150 pc for the ISM.

All observed HI features are reproduced in the simulation including the two 'concentrations' and two 'bridges'. In our model, M81 and M82 are both 4-component disk galaxies, including gas disks. A spherical galaxy model with a rotational gas component is chosen for the NGC3077. M82 is in a direct orbit with respect to the rotation of M81 and is found to impose a major disturbance to the extended gas component of M81. The orbit of NGC3077 is in retrograde and does not perturb M81 as significantly as does M82. On the other hand, NGC3077 is subjected to severe gas loss due to the tidal effect caused by M81. Mass-transfer induced activities, such as the starburst within M82 and at the centers of M81 and NGC3077, are also reproduced in our simulation. As the result of new constraints from radio observations, the extent of the M81 gas disk and the orbits of the two companions need to be modified from the previously known parameters to better reproduce the observed HI gas distribution.

This work was supported by the Pittsburgh Supercomputing Center, the National Center of Supercomputing Application, and the NASA's US ISO program.

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