Cosmic evolution of ETGs in Clusters
Galaxy clusters are incredible laboratories where to test the galaxy formation and evolution theories. They can give us a better insight about the role that environment plays in shaping galaxies over cosmic time, to try to solve the long-standing issue of nature vs. nurture. In addition, as they are formed by hundreds of galaxies, studying how the local properties vary over cosmic time is of great help to constrain the current evolution theories. However, going back in time is challenging, time-consuming and expensive. So far, most of the works at high redshift have used the stacking technique, in order to obtain a higher S/N and get the overall properties of galaxies.
I, however, have focused on studying and analyzing the stellar population properties of the individual galaxies for an intermediate-z cluster. This is the very first time an analysis like this has been performed in such detail. Therefore, we have characterized the ages, metallicities, abundance patterns and recovered the star formation histories for a set of ETGs in the cluster RX J0152.7 at z=0.83. We have found that we can trace back the formation of the cluster substructures via the SFHs of the ETGs that contain. The subclump that hosts the oldest and more massive galaxies, was formed first at high-z in a short episode, followed by a second subclump that presents similar galaxies, just a bit later in time, about 2Gyr later. Finally, we see that the outskirts are mostly populated by young, low-mass galaxies that present a residual SFH, indicative of their later incorporation in the cluster.
See:
A tale of a rich cluster at z~0.8 as een by the SFHs of its ETGs, A. Ferré-Mateu, P. Sánchez-Blåzquez, A. Vazdekis and I.G. de la Rosa, 2014, ApJ, 797, 136
ACS/WFC F625W/F775W/F850LP colour-composite image showing 5' of the RXJ0152.7-1357 mosaic eld. Figure from Blakeslee et al. (2006).
Position of the 24 ETGs in the central part of the cluster, formed by the North-subclump, the Shouth-subclump, the East-group and the outskirts. Galaxies are color-coded by the SFH type. From Ferré-Mateu et al. (2014)
We now have to extend this type of study to a larger sample of clusters and up to further redshifts, also using the information from the UV.
So stay tuned, more clusters at different redshifts are on the way!!!!!