Loss cone refilling by flyby encounters--A numerical study of massive
  black holes in galactic centres
  A gap in phase-space, the loss cone (LC), is opened up by a supermassive
black hole (MBH) as it disrupts or accretes stars in a galactic centre. If a
star enters the LC then, depending on its properties, its interaction with the
MBH will either generate a luminous electromagnetic flare or give rise to
gravitational radiation, both of which are expected to have directly observable
consequences. A thorough understanding of loss-cone refilling mechanisms is
important for the prediction of astrophysical quantities, such as rates of
tidal disrupting main-sequence stars, rates of capturing compact stellar
remnants and timescales of merging binary MBHs. In this thesis, we use N-body
simulations to investigate how noise from accreted satellites and other
substructures in a galaxy's halo can affect the LC refilling rate.
  Any N-body model suffers from Poisson noise which is similar to, but much
stronger than, the two-body diffusion occurring in real galaxies. To lessen
this spurious Poisson noise, we apply the idea of importance sampling to
develop a new scheme for constructing N-body realizations of a galaxy model, in
which interesting regions of phase-space are sampled by many low-mass
particles. We use multimass N-body models of galaxies with centrally-embedded
MBHs to study the effects of satellite flybys on LC refilling rates. We find
that although the flux of stars into the initially emptied LC is enhanced, but
the fuelling rate averaged over the entire subhalos is increased by only a
factor 3 over the rate one expects from the Poisson noise due the discreteness
of the stellar distribution.
