Title: Survey of Gravitationally-lensed Objects in HSC Imaging (SuGOHI). I. Automatic search for galaxy-scale strong lenses,
Abstract: The Hyper Suprime-Cam Subaru Strategic Program (HSC SSP) is an excellent
survey for the search for strong lenses, thanks to its area, image quality and
depth. We use three different methods to look for lenses among 43,000 luminous
red galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS) sample
with photometry from the S16A internal data release of the HSC SSP. The first
method is a newly developed algorithm, named YATTALENS, which looks for
arc-like features around massive galaxies and then estimates the likelihood of
an object being a lens by performing a lens model fit. The second method,
CHITAH, is a modeling-based algorithm originally developed to look for lensed
quasars. The third method makes use of spectroscopic data to look for emission
lines from objects at a different redshift from that of the main galaxy. We
find 15 definite lenses, 36 highly probable lenses and 282 possible lenses.
Among the three methods, YATTALENS, which was developed specifically for this
problem, performs best in terms of both completeness and purity. Nevertheless
five highly probable lenses were missed by YATTALENS but found by the other two
methods, indicating that the three methods are highly complementary. Based on
these numbers we expect to find $\sim$300 definite or probable lenses by the
end of the HSC SSP.