The AGEL Survey: Spectroscopic Confirmation of Strong Gravitational
  Lenses in the DES and DECaLS Fields Selected Using Convolutional Neural
  Networks
  We present spectroscopic confirmation of candidate strong gravitational
lenses using the Keck Observatory and Very Large Telescope as part of our ASTRO
3D Galaxy Evolution with Lenses (AGEL) survey. We confirm that 1) search
methods using Convolutional Neural Networks (CNN) with visual inspection
successfully identify strong gravitational lenses and 2) the lenses are at
higher redshifts relative to existing surveys due to the combination of deeper
and higher resolution imaging from DECam and spectroscopy spanning optical to
near-infrared wavelengths. We measure 104 redshifts in 77 systems selected from
a catalog in the DES and DECaLS imaging fields (r<22 mag). Combining our
results with published redshifts, we present redshifts for 68 lenses and
establish that CNN-based searches are highly effective for use in future
imaging surveys with a success rate of 88% (defined as 68/77). We report 53
strong lenses with spectroscopic redshifts for both the deflector and source
(z_src>z_defl), and 15 lenses with a spectroscopic redshift for either the
deflector (z_defl>0.21) or source (z_src>1.34). For the 68 lenses, the
deflectors and sources have average redshifts and standard deviations of
0.58+/-0.14 and 1.92+/-0.59 respectively, and corresponding redshift ranges of
(0.21<z_defl<0.89) and (0.88<z_src<3.55). The AGEL systems include 41
deflectors at zdefl>0.5 that are ideal for follow-up studies to track how mass
density profiles evolve with redshift. Our goal with AGEL is to
spectroscopically confirm ~100 strong gravitational lenses that can be observed
from both hemispheres throughout the year. The AGEL survey is a resource for
refining automated all-sky searches and addressing a range of questions in
astrophysics and cosmology.
