Constraints on the Size Evolution of Brightest Cluster Galaxies

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 fromclusters in the Einstein Medium Sensitivity Survey, five from the Las CampanasDistant Cluster Survey and its northern hemisphere precursor, and the remainingfour from traditional optical surveys. We find that the surface brightnessprofiles of all but three of these BCGs are well described by a standard deVaucouleurs ($r^{1/4}$) profile out to at least $\sim2r_{e}$ and that thebiweight-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 localBCG sample. If high redshift BCGs are in dynamical equilibrium and satisfy thesame scaling relations as low redshift ones, this change in size wouldcorrespond to a mass growth of a factor of 2 since $z \sim 0.5$. However, thebiweight-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 massaccretion rates higher than a factor of 2 in our sample, the discrepancybetween our NICMOS and WFPC2 results, which after various tests we describeappears to be physical, does not yet allow us to place strong constraints onaccretion rates below that level.Comment: ApJ accepted (566, 1, February 2002), 12 pages, uses emulateapj5.st