The Evolution of Mass-size Relation for Lyman Break Galaxies From z=1 to
  z=7
  For the first time, we study the evolution of the stellar mass-size relation
for star-forming galaxies from z ~ 4 to z ~ 7 from Hubble-WFC3/IR camera
observations of the HUDF and Early Release Science (ERS) field. The sizes are
measured by determining the best fit model to galaxy images in the rest-frame
2100 \AA \ with the stellar masses estimated from SED fitting to rest-frame
optical (from Spitzer/IRAC) and UV fluxes. We show that the stellar mass-size
relation of Lyman-break galaxies (LBGs) persists, at least to z ~ 5, and the
median size of LBGs at a given stellar mass increases towards lower redshifts.
For galaxies with stellar masses of 9.5<Log(M*/Msun)<10.4 sizes evolve as
$(1+z)^{-1.20\pm0.11}$. This evolution is very similar for galaxies with lower
stellar masses of 8.6<Log(M*/Msun)<9.5 which is $r_{e} \propto
(1+z)^{-1.18\pm0.10}$, in agreement with simple theoretical galaxy formation
models at high z. Our results are consistent with previous measurements of the
LBGs mass-size relation at lower redshifts (z ~ 1-3).
