  GN-z11 is the highest redshift galaxy spectroscopically confirmed with the
Hubble Space Telescope (HST). Previous measurements of the effective radius of
GN-z11 utilized galfit, which is not optimized to measure structural parameters
for such a faint, distant object. Using a new software program called forcepho
on HST data for the first time, we derive a size from images in the F160W band
obtained both from the complete CANDELS survey and additional midcycle
observations in order to contribute to the knowledge base on the size
evolution, size-luminosity, and size-mass relation of early galaxies. We find a
half-light radius mean of 0''.036 \(\pm\) 0''.006 corresponding to a physical
size of 0.15 \(\pm\) 0.025 kpc. This size, smaller than the point spread
function, is dramatically smaller than previous estimates with shallower HST
data using galfit but consistent with recent measurements using forcepho on new
JWST data arXiv:2302.07234. Such a small size, combined with the JWST/NIRSpec
spectroscopic observations arXiv:2305.12492, suggests that GN-z11's high
luminosity is dominated by an AGN.
