Stellar scattering and the formation of exponential discs in
  self-gravitating systems
  We show, using the N-body code GADGET-2, that stellar scattering by massive
clumps can produce exponential discs, and the effectiveness of the process
depends on the mass of scattering centres, as well as the stability of the
galactic disc. Heavy, dense scattering centres in a less stable disc generate
an exponential profile quickly, with a timescale shorter than 1 Gyr. The
profile evolution due to scattering can make a near-exponential disc under
various initial stellar distributions. This result supports analytic theories
that predict the scattering processes always favour the zero entropy gradient
solution to the Jeans/Poisson equations, whose profile is a near-exponential.
Profile changes are accompanied by disc thickening, and a power-law increase in
stellar velocity dispersion in both vertical and radial directions is also
observed through the evolution. Close encounters between stars and clumps can
produce abrupt changes in stellar orbits and shift stars radially. These events
can make trajectories more eccentric, but many leave eccentricities little
changed. On average, orbital eccentricities of stars increase moderately with
time.
