Seminário: Sistemas triplos de galáxias no SDSS

 

We present a new catalogue of galaxy triplets derived from the SDSS-DR7. The identification of systems was performed considering galaxies brighter than M_r=-20.5 and imposing constraints over the projected distances, radial velocity differences of neighbouring galaxies and isolation. We have used a mock catalogue to analyse the completeness and contamination of our methods. The results show a high level of completeness (~80%) and low contamination (~5%). By using photometric and spectroscopic data we have also addressed the effects of fiber collisions in the spectroscopic sample. We have defined an isolation criterion considering the distance of the triplet brightest galaxy to closest neighbour cluster, to describe a global environment, as well as the galaxies within a fixed aperture, around the triplet brightest galaxy, to measure the local environment. The final catalogue comprises 1092 isolated triplets of galaxies in the redshift range 0.01.