"Evolution of kinematics of early-type galaxies (ETGs) carries information about their assembly histories. However, direct observations of kinematics of high-redshift ETGs are difficult. In this study, we find a new photometric parameter which can be used as a proxy for kinematics, and investigate evolution of kinematics between z~1 and 0 using the parameter.
Firstly, by analyzing surface brightness profiles 166 non-barred ETGs from the ATLAS^3D survey, we find that slow rotators tend to have more extended profiles in outer regions than fast rotators compared at the same stellar mass. We define a new photometric parameter, ∆Slope, with which the extendedness of the outer profile is quantified. We find a good correlation between ∆Slope and spin parameters (λ and V/σ) and obtain the best fitted linear relations between ∆Slope and the spin parameters.
Then, we measured ∆Slope of ~600 cluster ETGs respectively at z~1 and 0, using imaging data from Hubble Space Telescope (z~1) and Sloan Digital Sky Survey (z~0) with appropriate correction for the point spread function. For ETGs with 10 < log(M*/Msun) < 11, we find significant evolution of ∆Slope. The relation between ∆Slope and spin parameters indicates that high-redshift ETGs rotates more rapidly than low-redshift counterparts. We do not find significant evolution for massive ETGs (log(M*/Msun) > 11). The results should be compared with future direct observations. We are now developing a next generation adoptive optics system for the Subaru telescope aiming to obtain spatially resolved stellar kinematics of high-redshift galaxies."