RELICS: Properties of z>5.5 Galaxies Inferred from Spitzer and Hubble
  Imaging Including A Candidate z~6.8 Strong [OIII] Emitter
  We present constraints on the physical properties (including stellar mass,
age, and star formation rate) of 207 $6\lesssim z \lesssim8$ galaxy candidates
from the Reionization Lensing Cluster Survey (RELICS) and companion
Spitzer-RELICS surveys. We measure photometry using T-PHOT and perform spectral
energy distribution fitting using EA$z$Y and BAGPIPES. Of the 207 candidates
for which we could successfully measure Spitzer fluxes, 23 were demoted to
likely low redshift ($z<4$). Among the remaining high redshift candidates, we
find intrinsic stellar masses between $1\times10^6\rm{M_{\odot}}$ and
$4\times10^9\rm{M_\odot}$, and rest-frame UV absolute magnitudes between
$-22.6$ and $-14.5$ mag. While our sample is mostly comprised of
$L_{UV}/L^*_{UV}<1$ galaxies, there are a number of brighter objects in the
sample, extending to $L_{UV}/L^*_{UV}\sim2$. The galaxies in our sample span
approximately four orders of magnitude in stellar mass and star-formation
rates, and exhibit ages ranging from maximally young to maximally old. We
highlight 11 galaxies which have detections in Spitzer/IRAC imaging and
redshift estimates $z\geq6.5$, several of which show evidence for some
combination of evolved stellar populations, large contributions of nebular
emission lines, and/or dust. Among these is PLCKG287+32-2013, one of the
brightest $z\sim7$ candidates known (AB mag 24.9) with a Spitzer 3.6$\mu$m flux
excess suggesting strong [OIII] + H-$\beta$ emission ($\sim$1000\AA\ rest-frame
equivalent width). We discuss the possible uses and limits of our sample and
present a public catalog of Hubble 0.4--1.6$\mu$m + Spitzer 3.6$\mu$m and
4.5$\mu$m photometry along with physical property estimates for all 207 objects
in the sample. Because of their apparent brightnesses, high redshifts, and
variety of stellar populations, these objects are excellent targets for
follow-up with James Webb Space Telescope.
