## NBODY6

It was 5 years ago when I had run NBODY6 last time. Since I didn’t backup the data carefully, It takes times to recover my memory. Anyway I did two projects using NBODY6, direct numerical integration code developed by Dr. Sverre Aarseth.

1. I modified the code to simulate the rotating star cluster. In our(Eunhyeuk Kim, Ilsang Yoon, Hyung Mok Lee and Rainer Spurzem) paper, we compared NBODY6 and Fokker Planck method for rotating star cluster simulation and confirmed that they agree pretty well, although detail features might be different due to the natures of these two methods. Core collapse is accelerated via Gravo-gyro catastrophe which is a similar concept with Gravothermal catastrophe. We speculated that the detail difference between the results from these two method is from the existence of third integral, which may be manifested in direct particle simulation using NBODY6, but not in Fokker Planck model of rotating star cluster. This is for only single mass model(every particle has same mass). Now we are trying to extend this study to multi-mass model. This is actually done in the original draft 5 years ago. Now I am trying to re-simulate multi-mass rotating star cluster since I lost the data for multi-mass model. For recovering my memory, the following web page will be useful.

http://nbodylab.interconnect.com/

2. I proposed a new equilibrium model of self gravitating system embedded in external potential well and compared the analytical result with numerical simulation using NBODY6. Due to the nature of gravity, the thermodynamical description of self-gravitating system is a good approximation only in few limited cases. We (me and my advisor) posed the dynamical evolution of self-gravitating system in the center of external potential well. Using the assumption of constant temperature at the boundary, we derived the equilibrium model with different ratios of potential depth of the system and the surrounding external potential. And we studied the dynamical evolution of embedded stellar system in the external potential well. We expect that this study might give us an insight about the dynamical evolution of galaxy cluster, of which member galaxies are moving around under the deep dark matter potential well. This was my master thesis. I didn’t have enough time to push it for publication, but sooner of later, I will start to work on it.