MUSE spectroscopy and deep observations of a unique compact JWST target,
  lensing cluster CLIO
  We present the results of a VLT MUSE/FORS2 and Spitzer survey of a unique
compact lensing cluster CLIO at z = 0.42, discovered through the GAMA survey
using spectroscopic redshifts. Compact and massive clusters such as this are
understudied, but provide a unique prospective on dark matter distributions and
for finding background lensed high-z galaxies. The CLIO cluster was identified
for follow up observations due to its almost unique combination of high mass
and dark matter halo concentration, as well as having observed lensing arcs
from ground based images. Using dual band optical and infra-red imaging from
FORS2 and Spitzer, in combination with MUSE optical spectroscopy we identify 89
cluster members and find background sources out to z = 6.49. We describe the
physical state of this cluster, finding a strong correlation between
environment and galaxy spectral type. Under the assumption of a NFW profile, we
measure the total mass of CLIO to be M$_{200} = (4.49 \pm 0.25) \times 10^{14}$
M$_\odot$. We build and present an initial strong-lensing model for this
cluster, and measure a relatively low intracluster light (ICL) fraction of 7.21
$\pm$ 1.53% through galaxy profile fitting. Due to its strong potential for
lensing background galaxies and its low ICL, the CLIO cluster will be a target
for our 110 hour JWST 'Webb Medium-Deep Field' (WMDF) GTO program.
