Radio Galaxy Zoo: Observational evidence for environment as the cause of
  radio source asymmetry
  We investigate the role of environment on radio galaxy properties by
constructing a sample of large ($\gtrsim100$~kpc), nearby ($z<0.3$) radio
sources identified as part of the Radio Galaxy Zoo citizen science project. Our
sample consists of 16 Fanaroff-Riley Type II (FR-II) sources, 6 FR-I sources,
and one source with a hybrid morphology. FR-I sources appear to be hosted by
more massive galaxies, consistent with previous studies. In the FR-II sample,
we compare the degree of asymmetry in radio lobe properties to asymmetry in the
radio source environment, quantified through optical galaxy clustering. We find
that the length of radio lobes in FR-II sources is anti-correlated with both
galaxy clustering and lobe luminosity. These results are in quantitative
agreement with predictions from radio source dynamical models, and suggest that
galaxy clustering provides a useful proxy for the ambient gas density
distribution encountered by the radio lobes.
