Tesis Doctorado
On the formatión epoch of cluster galaxies and the growth of the red-sequence from a sample of rich clusters at z - 1.
Autor
Barrientos, Luis Felipe
Pontificia Universidad Católica de Chile
Institución
Resumen
Galaxy clusters, the most massive virialized structures in the Universe, are ideal systems to study the formation and evolution of galaxies in high density environments.
Their cores are dominated by early-type galaxies, which traditionally are considered as dynamically simple stellar systems, and whose stellar populations can
be modeled by a single burst of star formation at redshifts higher than 2. This thesis work aims to understand the formation and evolution of early-type galaxies that
inhabit rich galaxy clusters.
In the first part, we study the formation epoch at which central cluster galaxies formed the bulk of their stellar content. For this purpose, we built the K-band
luminosity function of cluster galaxies for a combined sample of 15 clusters located about redshift one, through the application of a statistical background subtraction
method. This luminosity function is well represented by a Schechter function of characteristic magnitude K* = 18.82tg, and faint-end siope a = —0.42t. W hen
the value of the faint-end siope is fixed to a = —0.9, we obtain a change in the characteristic magnitude of LK* = 7.49 between redshifts z=1 and 0.023, which is consistent with the predictions of a passive evolution model for an L* galaxy formed at redshift zf = 3.
In the second part, we study the build-up of the red-sequence in rich clusters since z=1. We computed the J-K color-magnitude relation of early-type galaxies at
z=1 for a sample of 5 galaxy clusters with morphological classification from Hubble Space Telescope (HST) images, and we obtained that its best-fit linear model has
siope of —0.05 + 0.01. We built the background subtracted color-magnitude diagram of cluster galaxies for a combined sample of 15 clusters located about redshift one,
and qualitatively determined a deficit of faint red-sequence galaxies relative to bright ones in clusters at z=1. We measured, for the first time, the luminous-to-faint ratio
of red-sequence galaxies at z=1 from a large ensemble of clusters, and found an increase of 100% in the ratio of luminous-to-faint red-sequence galaxies from redshift
z=0.45 to 1.0. Finally, the measured change in this ratio as function of redshift is well-reproduced by a simple evolutionary model developed in this work that consists
in an early truncation of the star formation for bright cluster galaxies and a delayed truncation for faint cluster galaxies.