Survey of Gravitationally Lensed Objects in HSC Imaging (SuGOHI). II. Environments and Line-of-Sight Structure of Strong Gravitational Lens Galaxies to z similar to 0.8

We investigate the local and line-of-sight (LOS) 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(L) similar to 0.8, we compare galaxy number counts in LOSs toward known and newly discovered lenses in the survey to those of a control sample consisting of random LOSs. We also compare the local overdensity of lens galaxies to a sample of "twin" galaxies that have similar redshift and velocity dispersion to test whether lenses lie in different environments from similar nonlens 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 LOSs 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.