Tracing the gravitational potential using cosmic voids
  The properties of large underdensities in the distribution of galaxies in the
Universe, known as cosmic voids, are potentially sensitive probes of
fundamental physics. We use data from the MultiDark suite of N-body simulations
and multiple halo occupation distribution mocks to study the relationship
between galaxy voids, identified using a watershed void-finding algorithm, and
the gravitational potential $\Phi$. We find that the majority of galaxy voids
correspond to local density minima in larger-scale overdensities, and thus lie
in potential wells. However, a subset of voids can be identified that closely
trace maxima of the gravitational potential and thus stationary points of the
velocity field. We identify a new void observable, $\lambda_v$, which depends
on a combination of the void size and the average galaxy density contrast
within the void, and show that it provides a good proxy indicator of the
potential at the void location. A simple linear scaling of $\Phi$ as a function
of $\lambda_v$ is found to hold, independent of the redshift and properties of
the galaxies used as tracers of voids. We provide an accurate fitting formula
to describe the spherically averaged potential profile $\Phi(r)$ about void
centre locations. We discuss the importance of these results for the
understanding of the evolution history of voids, and for their use in precision
measurements of the integrated Sachs-Wolfe effect, gravitational lensing and
peculiar velocity distortions in redshift space.
