Survey of Gravitationally-lensed Objects in HSC Imaging (SuGOHI). II.
  Environments and Line-of-Sight Structure of Strong Gravitational Lens
  Galaxies to z ~ 0.8
  We investigate the local and line-of-sight overdensities of strong
gravitational lens galaxies using wide-area multiband imaging from the Hyper
Suprime-Cam Subaru Strategic Program. We present 41 new definite or probable
lens candidates discovered in Data Release 2 of the survey. Using a combined
sample of 87 galaxy-scale lenses out to a lens redshift of $z_{\mathrm{L}} \sim
0.8$, we compare galaxy number counts in lines of sight toward known and
newly-discovered lenses in the survey to those of a control sample consisting
of random lines of sight. We also compare the local overdensity of lens
galaxies to a sample of "twin" galaxies that have a similar redshift and
velocity dispersion to test whether lenses lie in different environments from
similar non-lens galaxies. We find that lens fields contain higher number
counts of galaxies compared to the control fields, but this effect arises from
the local environment of the lens. Once galaxies in the lens plane are removed,
the lens lines of sight are consistent with the control sample. The local
environments of the lenses are overdense compared to the control sample, and
are slightly overdense compared to those of the twin sample, although the
significance is marginal. There is no significant evidence of the evolution of
the local overdensity of lens environments with redshift.
