Evolution of the Galaxy Cluster Red Sequence from Redshift 0.2 to 1.5

Abstract

In this thesis, we present a study of the population of early-type galaxies in 115 clusters at 0.2 < z < 1.5, imaged with the F200LP/UVIS and F110W/IR filters of the Wide Field Camera 3 on the Hubble Space Telescope. We aim to investigate the evolution of the red sequence parameters (zero-point, slope, and intrinsic scatter) in the color-magnitude plane to constrain its members’ history and epoch of star formation. To accomplish this, we carefully selected the galaxies belonging to the red sequence, dismissing all contamination from the background and late-type galaxies into the clusters. Then, we used a robust linear fitting method to obtain the red sequence parameters in the rest frame. Finally, we compared the evolution of the zero-point with that of the color in stellar population synthesis models with different metallicity, formation red-shift, and e-folding time. We find that, as the redshift increases, the zero-point moves towards blue, the slope becomes steeper, and the observed scatter increases. On the other hand, the mean color of the clusters evolves slowly and is highly similar in systems at the same redshift, located in random directions in the universe. Therefore, the change of the zero-point is in agreement with the passive evolution of early galaxies in the present cosmological scenario. At the same time, we attribute the slope evolution to archaeological downsizing in conjunction with the progressive build-up of the red sequence. Finally, we constrain the epoch and period of stellar population formation to a strip diagonally crossing the τ - zf plane.