Three-Dimensional Moving-Mesh Simulations of Galactic Center Cloud G2
  Using three-dimensional, moving-mesh simulations, we investigate the future
evolution of the recently discovered gas cloud G2 traveling through the
galactic center. We consider the case of a spherical cloud initially in
pressure equilibrium with the background. Our suite of simulations explores the
following parameters: the equation of state, radial profiles of the background
gas, and start times for the evolution. Our primary focus is on how the fate of
this cloud will affect the future activity of Sgr A*. From our simulations we
expect an average feeding rate in the range of $5-19 \times 10^{-8}$ solar
masses per year beginning in 2013 and lasting for at least 7 years (our
simulations stop in year 2020). The accretion varies by less than a factor of
three on timescales <1 month, and shows no more than a factor of 10 difference
between the maximum and minimum. These rates are comparable to the current
estimated accretion rate in the immediate vicinity of Sgr A*, although they
represent only a small (<5%) increase over the current expected feeding rate at
the effective inner boundary of our simulations. Therefore, the break up of
cloud G2 may have only a minimal effect on the brightness and variability of
Sgr A* over the next decade. This is because current models of the galactic
center predict that most of the gas will be caught up in outflows. However, if
the accreted G2 material can remain cold, it may not mix well with the hot,
diffuse background gas, and instead accrete efficiently onto Sgr A*. Further
observations of G2 will give us an unprecedented opportunity to test this idea.
The break up of the cloud itself may also be observable. By tracking the amount
of cloud energy that is dissipated during our simulations, we are able to get a
rough estimate of the luminosity associated with its tidal disruption; we find
values of a few $10^{36}$ erg/s.
