RELICS: Strong Lensing Analysis of MACS J0417.5-1154 and Predictions for
  Observing the Magnified High-Redshift Universe with JWST
  Strong gravitational lensing by clusters of galaxies probes the mass
distribution at the core of each cluster and magnifies the universe behind it.
MACS J0417.5-1154 at z=0.443 is one of the most massive clusters known based on
weak lensing, X-ray, and Sunyaev-Zel'dovich analyses. Here we compute a strong
lens model of MACS J0417 based on Hubble Space Telescope imaging observations
collected, in part, by the Reionization Lensing Cluster Survey (RELICS), and
recently reported spectroscopic redshifts from the MUSE instrument on the Very
Large Telescope (VLT). We measure an Einstein radius of ThetaE=36'' at z = 9
and a mass projected within 200 kpc of M(200 kpc) = 1.78+0.01-0.03x10**14Msol.
Using this model, we measure a ratio between the mass attributed to
cluster-member galaxy halos and the main cluster halo of order 1:100. We assess
the probability to detect magnified high-redshift galaxies in the field of this
cluster, both for comparison with RELICS HST results and as a prediction for
the James Webb Space Telescope (JWST) Guaranteed Time Observations upcoming for
this cluster. Our lensing analysis indicates that this cluster has similar
lensing strength to other clusters in the RELICS program. Our lensing analysis
predicts a detection of at least a few z~6-8 galaxies behind this cluster, at
odds with a recent analysis that yielded no such candidates in this field.
Reliable strong lensing models are crucial for accurately predicting the
intrinsic properties of lensed galaxies. As part of the RELICS program, our
strong lensing model produced with the Lenstool parametric method is publicly
available through the Mikulski Archive for Space Telescopes (MAST).
