IAU Symposium Abstract S186-043P

Spin angular momentum of merger remnants of spherical galaxies

Indian Institute of Astrophysics Bangalore 560034 India < pmsn@iiap.ernet.in >

Numerical simulations of both merging and non-merging collisions of equal mass spherical galaxies have been performed to study the effect of varying the impact parameter on the behaviour of induced spin in the merger remnants. The transition from merging to non-merging occurs in a narrow range in impact parameter. The transfer of orbital angular momentum to the internal spin shows a sharp decrease after the galaxies cross the pericentric point. Even though the effective mass loss is 10 per cent, more than 85 per cent of the transferred spin is absorbed by the escaping particles. In highly energetic collisions, the amount of spin carried away by the escaping mass is less than 60 per cent and consequently yield remnants with rotation characteristic of a typical elliptical galaxy. In other collisions, the residual spin is not enough to induce appreciable rotation. The direction of the remnant spin vector is seen to be perfectly aligned with the direction of the initial orbital angular momentum of the pair.