We measure the luminosity profiles of 16 brightest cluster galaxies ( BCGs ) at 0.4 < z < 0.8 using high resolution F160W NICMOS and F814W WFPC2 HST imaging .
The heterogeneous sample is drawn from a variety of surveys : seven from clusters in the Einstein Medium Sensitivity Survey ( EMSS ; 17 ) , five from the Las Campanas Distant Cluster Survey and its northern hemisphere precursor ( LCDCS ; 11 ; 18 ; 31 ) , and the remaining four from traditional optical surveys ( 48 ; 25 ; 20 ; 10 ) .
We find that the surface brightness profiles of all but three of these BCGs are well described by a standard de Vaucouleurs ( r ^ { 1 / 4 } ) profile out to at least \sim 2 r _ { e } and that the biweight-estimated NICMOS effective radius of our high redshift BCGs ( r _ { e } = 8.3 \pm 1.4 kpc for H _ { 0 } = 80 km s ^ { -1 } Mpc ^ { -1 } , \Omega _ { m } = 0.2 , \Omega _ { \Lambda } = 0.0 ) is \sim 2 times smaller than that measured for a local BCG sample ( 19 ) .
If high redshift BCGs are in dynamical equilibrium and satisfy the same scaling relations as low redshift ones , this change in size would correspond to a mass growth of a factor of 2 since z \sim 0.5 .
However , the biweight-estimated WFPC2 effective radius of our sample is 18 \pm 5.1 kpc , which is fully consistent with the local sample .
While we can rule out mass accretion rates higher than a factor of 2 in our sample , the discrepancy between our NICMOS and WFPC2 results , which after various tests we describe appears to be physical , does not yet allow us to place strong constraints on accretion rates below that level .