We present high-resolution imaging in the rest-frame optical of the weak radio source LBDS53W091 .
Previous optical spectroscopy has shown that this object has an evolved stellar population of age > 3 Gyr at z = 1.55 , determined from the amplitude of rest-frame UV spectral breaks .
We have obtained deep Hubble Space Telescope imaging over 10 orbits with NICMOS camera 2 , using the F160W H -band filter ( 1.6 \mu m ) which is a good approximation to the rest-frame R -band .
Our observations reveal a radial light profile which is well fit by a de Vaucouleurs ’ r ^ { 1 / 4 } law , with a scale length of r _ { e } = 0.3 ^ { \prime \prime } ( 3 h _ { 50 } ^ { -1 } kpc for \Omega _ { M } = 0.3 and \Omega _ { \Lambda } = 0 ) .
The elliptical morphology of the radio galaxy indicates a dynamically-evolved old system , consistent with the spectroscopic results .
Some surrounding objects lie on the color : magnitude relation for a cluster at z = 1.55 , and are likely to be associated .
The group of galaxies are somewhat more luminous than the fundamental plane of ellipticals at z = 0 subject to ( 1 + z ) ^ { 4 } surface brightness dimming , but are consistent with estimates of the fundamental plane at high redshift subject to passive luminosity evolution from a formation epoch of z > 3 . abstract