  Many star-forming galaxies and those hosting active galactic nuclei (AGN)
show evidence of massive outflows of material in a variety of phases including
ionized, neutral atomic, and molecular. Molecular outflows in particular have
been the focus of recent interest as they may be responsible for removing gas
from the galaxy, thereby suppressing star formation. As material is ejected
from the cores of galaxies, interactions of the outflowing material with the
interstellar medium can accelerate cosmic rays and produce high-energy gamma
rays. In this work, we search for gamma-ray emission from a sample of local
galaxies known to host molecular outflows using data collected by the {\fermi}
Large Area Telescope. We employ a stacking technique in order to search for and
characterize the average gamma-ray emission properties of the sample. Gamma-ray
emission is detected from the galaxies in our sample at the $4.4 \, \sigma$
level with a power-law photon index of $\Gamma \approx 2$ in the 1-800 GeV
energy range. The emission is found to correlate with tracers of star formation
activity, namely the $8-1000 \: \mu$m infrared luminosity. We also find that
the observed signal can be predominantly attributed to \ion{H}{ii} galaxies
hosting energy-driven outflows. While we do not find evidence suggesting that
the outflows are accelerating charged particles directly, galaxies with
molecular outflows may produce more gamma rays than galaxies without outflows.
In particular, the set consisting of gamma-ray-detected galaxies with molecular
outflows are nearly perfect calorimeters and may be future targets for searches
of high-energy neutrinos.
