  The first deep-field observations of the JWST have immediately yielded a
surprisingly large number of very high redshift candidates, pushing the
frontier of observability well beyond $z\gtrsim10$. We here present a detailed
SED-fitting analysis of the 15 gravitationally lensed $z\sim10-16$ galaxy
candidates detected behind the galaxy cluster SMACS J0723.3-7327 in Atek et al.
(2022) using the BEAGLE tool. Our analysis makes use of dynamical
considerations to place limits on the ages of these galaxies and of all three
published SL models of the cluster to account for lensing systematics. We find
these galaxies to have relatively low stellar masses
$M_{\star}\sim10^7-10^8\,\mathrm{M}_{\odot}$ and young ages
$t_{\mathrm{age}}\sim10-100$\,Myr. Due to their very blue UV-slopes, down to
$\beta\sim-3$, all of the galaxies in our sample have extremely low dust
attenuations $A_V\lesssim0.02$. Placing the measured parameters into relation,
we find a very shallow $M_{\star}-M_{\mathrm{UV}}$-slope and high sSFRs above
the main sequence of star-formation with no significant redshift-evolution in
either relation. This is in agreement with the bright UV luminosities measured
for these objects and indicates that we are naturally selecting galaxies that
are currently undergoing a star-bursting episode at the time they are observed.
Finally, we discuss the robustness of our high-redshift galaxy sample regarding
low-redshift interlopers and conclude that low-redshift solutions can safely be
ruled out for roughly half of the sample, including the highest-redshift
galaxies at $z\sim12-16$. These objects represent compelling targets for
spectroscopic follow-up observations with JWST and ALMA.
