Size-mass relation of the brightest cluster galaxies at z ∼ 1

We present the size-mass relation of the brightest cluster galaxies (BCGs) at 0.1 < z < 1.4 using the imaging data obtained by the Hyper Suprime-Cam Subaru Strategic Program. Our sample consists of 471 photometrically selected BCGs with stellar mass logM(*)/M-circle dot = 11-12. We measure the size of the BCGs using i-band imaging and model fits based on a single S & eacute;rsic light profile. Stellar masses are determined through spectral energy distribution fitting using S & eacute;rsic-modelled photometry data across five optical bands (grizy). The size-mass scaling relation of BCGs is $r_\mathrm{ e}\propto M_*<^>{0.73-1.00}$ at z < 1, with a slope that does not evolve significantly. The slope of the size-mass relation for BCGs is steeper than other non-BCG galaxies, which implies that BCGs are a special galaxy population. The size of BCGs at a given stellar mass evolves rapidly as proportional to (1 + z)(-1.58 +/- 0.13) and increases with redshift by a factor of 2.5 from z similar to 1.2 to z similar to 0.2. The rapid size growth is in agreement with semi-analytical model results, indicating that the BCG growth is dominated by frequent minor mergers. Furthermore, we explore the size-mass relationship of BCGs with respect to the halo mass of the cluster and find there is no significant correlation, which might imply that a dependence on the environment predominantly affects the outer envelope of the BCGs.