  We analyzed the contribution of the intracluster light (ICL) to the total
luminosity of two massive galaxy clusters observed by the Hubble Space
Telescope within the Frontier Fields program, Abell 370 (z ~ 0.375) and Abell
S1063 (z ~ 0.348), in order to correlate it with the dynamical stage of these
systems.We applied an algorithm based on the Chebyshev-Fourier functions called
CICLE, specially developed to disentangle the ICL from the light of galaxies
and measure the ICL fraction. We measured the ICL fraction in three broadband
optical filters, F435W, F606W, and F814W, without assuming any prior hypothesis
about the ICL physical properties or morphology. The results obtained from the
ICL fraction vary between ~7% - 25%, and ~3% - 22% for both A370 and AS1063,
respectively, which are consistent with theoretical predictions for the total
amount of ICL obtained by ICL formation and evolution simulations.We found
enhanced ICL fractions in the intermediate filter F606W for both clusters and
we suggest that this is due to the presence of an excess of
younger/lower-metallicity stars in the ICL compared to the cluster galaxies. We
conclude that both Abell 370 and Abell S1063 are merging systems since they
exhibit a similar feature as merging CLASH and Frontier Fields clusters
sub-sample previously analyzed. We compare these results to the dynamical
indicators obtained through different methods and we reinforce the use of ICL
as a new and independent method to determine the dynamical state of clusters of
galaxies.
