The data here may be slightly different than the ones in other similar archives (e.g. GC3). The 81920 particles are in the following order:
16384 Gal. disk 16384 And. disk 8192 Gal. bulge 8192 And. bulge 16384 Gal. halo 16384 And. haloThese initial conditions start at a point less than 1 Gyr before the collision since during the 3-4 Gyr or so leading up to the collision nothing much happens. So Andromeda should look bigger than it is at the moment. The simulation starts when Andromeda is only about 120 kpc away from the Galaxy instead of the current 700 kpc so it should look about 5 times bigger than it looks now.
In NEMO this table can be read into a snapshot as follows:
zcat dubinski.tab.gz |\ tabtos - m31.ini block1=m,pos,vel nbody=81920 times=0If you want to run a quick simulation, you could take a subset of the particles, multiply the masses appropriately and integrate, a subset of 640 particles, (320 per galaxy: 128 disk, 64 bulge, 128 halo):
zcat dubinski.tab.gz |\ tabtos - - block1=m,pos,vel nbody=81920 times=0 |\ snapcopy - - select=i%128 |\ snapscale - m31_small.ini mscale=128 hackcode1 m31_small.ini m31_small.dat tstop=80 freqout=1 > m31_small.log