The Sloan Lens ACS Survey. XIII. Discovery of 40 New Galaxy-Scale Strong
  Lenses
  We present the full sample of 118 galaxy-scale strong-lens candidates in the
Sloan Lens ACS (SLACS) Survey for the Masses (S4TM) Survey, which are
spectroscopically selected from the final data release of the Sloan Digital Sky
Survey. Follow-up Hubble Space Telescope (HST) imaging observations confirm
that 40 candidates are definite strong lenses with multiple lensed images. The
foreground lens galaxies are found to be early-type galaxies (ETGs) at
redshifts 0.06 to 0.44, and background sources are emission-line galaxies at
redshifts 0.22 to 1.29. As an extension of the SLACS Survey, the S4TM Survey is
the first attempt to preferentially search for strong-lens systems with
relatively lower lens masses than those in the pre-existing strong-lens
samples. By fitting HST data with a singular isothermal ellipsoid model, we
find total projected mass within the Einstein radius of the S4TM strong-lens
sample ranges from $3 \times10^{10} M_{\odot}$ to $2 \times10^{11} M_{\odot}$.
In [Shu15], we have derived the total stellar mass of the S4TM lenses to be $5
\times10^{10} M_{\odot}$ to $1 \times10^{12} M_{\odot}$. Both total enclosed
mass and stellar mass of the S4TM lenses are on average almost a factor of 2
smaller than those of the SLACS lenses, which also represent typical mass
scales of the current strong-lens samples. The extended mass coverage provided
by the S4TM sample can enable a direct test, with the aid of strong lensing,
for transitions in scaling relations, kinematic properties, mass structure, and
dark-matter content trends of ETGs at intermediate-mass scales as noted in
previous studies.
