- Nombre : THE CD GALAXY - CD HALO CONNECTION
- Número/Código : G/2011A/017
- Nombre Concurso : CONCURSO PROPUESTAS DE OBSERVACIÓN ASTRONÓMICA PARA TIEMPO CHILENO EN EL OBSERVATORIO GEMINI SUR 2011A
- Año Concurso : 2011
- Tiempo asignado : 12,17 HORAS
The formation mechanism of cD galaxies and their extended stellar envelopes still holds mysteries. Many processes, not necessarily exclusive, can be at play: stellar formation at the bottom of cooling flows, galactic cannibalism, hierarchical merging, etc. The existence of cD galaxies exhibiting significant peculiar velocities respect to their parent cluster mean velocity is difficult to reconcile with scenarios requiring the galaxy to be formed at the bottom of the potential well. Even though galaxies can be formed outside the cluster and then be accreted, this cannot happen with cD halos which would not survive the accretion process due to tidal truncation. These "moving" cDs raise the following questions: are central galaxies kinematically coupled to their halos? Can cD-halos form independently in the central regions of a galaxy cluster which a galaxy occupies through infall? In this proposal we aim at the clusters A3653 and A2670, which present the most extreme cases of "moving" cDs. Deep, extended spectroscopy of their central galaxies will allow us to measure mean velocity and velocity dispersion profiles as well as ages and metallicities of the galaxies and their cD halos, helping us to answer the question whether these galaxies and halos share a common origin.