Mass Transport and Turbulence in Gravitationally Unstable Disk Galaxies
  II: The Effects of Star Formation Feedback
  Self-gravity and stellar feedback are capable of driving turbulence and
transporting mass and angular momentum in disk galaxies, but the balance
between them is not well understood. In the previous paper in this series, we
showed that gravity alone can drive turbulence in galactic disks, regulate
their Toomre $Q$ parameters to $\sim$ 1, and transport mass inwards at a rate
sufficient to fuel star formation in the centers of present-day galaxies. In
this paper we extend our models to include the effects of star formation
feedback. We show that feedback suppresses galaxies' star formation rates by a
factor of $\sim$ 5 and leads to the formation of a multi-phase atomic and
molecular ISM. Both the star formation rate and the phase balance produced in
our simulations agree well with observations of nearby spirals. After our
galaxies reach steady state, we find that the inclusion of feedback actually
lowers the gas velocity dispersion slightly compared to the case of pure
self-gravity, and also slightly reduces the rate of inward mass transport.
Nevertheless, we find that, even with feedback included, our galactic disks
self-regulate to $Q$ $\sim$ 1, and transport mass inwards at a rate sufficient
to supply a substantial fraction of the inner disk star formation. We argue
that gravitational instability is therefore likely to be the dominant source of
turbulence and transport in galactic disks, and that it is responsible for
fueling star formation in the inner parts of galactic disks over cosmological
times.
