The Large-scale Effect of Environment on Galactic Conformity
  We use a volume-limited galaxy sample from the SDSS Data Release 7 to explore
the dependence of galactic conformity on the large-scale environment, measured
on $\sim$ 4 Mpc scales. We find that the star formation activity of neighbour
galaxies depends more strongly on the environment than on the activity of their
primary galaxies. In under-dense regions most neighbour galaxies tend to be
active, while in over-dense regions neighbour galaxies are mostly passive,
regardless of the activity of their primary galaxies. At a given stellar mass,
passive primary galaxies reside in higher density regions than active primary
galaxies, leading to the apparently strong conformity signal. The dependence of
the activity of neighbour galaxies on environment can be explained by the
corresponding dependence of the fraction of satellite galaxies. Similar results
are found for galaxies in a semi-analytical model, suggesting that no new
physics is required to explain the observed large-scale conformity.
