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Roberto Muñoz |
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"The growth of the
red-sequence in clusters since z~1" |
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Galaxy clusters are gravitationally bounded structures in the Universe, which are inhabited by several thousands of galaxies in a very small region in the sky and filled by a hot X-ray emitting gas. The central megaparsec of clusters is dominated by early type galaxies, which are observed to obey tight empirical scaling relations as the Fundamental plane and the Red-sequence. In this work, we present deep Js and Ks-band imaging of 15 galaxy clusters at $z\simeq 1$, which were discovered in the Red-Sequence Cluster Survey (RCS-1) and followed up using the VLT/ISAAC instrument. We built the Ks-band luminosity function for the composite cluster down to $M^*+2.5$ through the application of a background subtraction method, and we found that it can be described by a Schechter function with $K_s^*=18.82$ and $\alpha =-0.42$. Furthermore, we built the background subtracted color-magnitude diagram for the composite cluster and measured for the first time the ratio of luminous-to-faint red-sequence galaxies at $z=1$ from a large ensemble of clusters. We found an increase of 100\% in this ratio from z=0.45 to 1.0, that can be explained by a simple evolutionary model developed in this work consisting in an early truncation of the star formation for bright cluster galaxies and a delayed truncation for faint cluster galaxies. |