The Grism Lens-Amplified Survey from Space (GLASS). VI. Comparing the
  Mass and Light in MACSJ0416.1-2403 using Frontier Field imaging and GLASS
  spectroscopy
  We present a strong and weak gravitational lens model of the galaxy cluster
MACSJ0416.1-2403, constrained using spectroscopy from the Grism Lens-Amplified
Survey from Space (GLASS) and Hubble Frontier Fields (HFF) imaging data. We
search for emission lines in known multiply imaged sources in the GLASS
spectra, obtaining secure spectroscopic redshifts of 31 multiple images
belonging to 16 distinct source galaxies. The GLASS spectra provide the first
spectroscopic measurements for 6 of the source galaxies. The weak lensing
signal is acquired from 884 galaxies in the F606W HFF image. By combining the
weak lensing constraints with 15 multiple image systems with spectroscopic
redshifts and 9 multiple image systems with photometric redshifts, we
reconstruct the gravitational potential of the cluster on an adaptive grid. The
resulting total mass density map is compared with a stellar mass density map
obtained from the deep Spitzer Frontier Fields imaging data to study the
relative distribution of stellar and total mass in the cluster. We find that
the projected stellar mass to total mass ratio, $f_{\star}$, varies
considerably with the stellar surface mass density. The mean projected stellar
mass to total mass ratio is $\langle f_{\star} \rangle= 0.009 \pm 0.003 $
(stat.), but with a systematic error as large as $0.004-0.005$, dominated by
the choice of the IMF. We find agreement with several recent measurements of
$f_{\star}$ in massive cluster environments. The lensing maps of convergence,
shear, and magnification are made available to the broader community in the
standard HFF format.
