Spatial environment of polar-ring galaxies from the SDSS
  Based on SDSS data, we have considered the spatial environment of galaxies
with extended polar rings. We used two approaches: estimating the projected
distance to the nearest companion and counting the number of companions as a
function of the distance to the galaxy. Both approaches have shown that the
spatial environment of polar-ring galaxies on scales of hundreds of kiloparsecs
is, on average, less dense than that of galaxies without polar structures.
Apparently, one of the main causes of this effect is that the polar structures
in a denser environment are destroyed more often during encounters and mergers
with other galaxies.
