Satellites and central galaxies in SDSS: the influence of interactions
  on their properties
  We use SDSS-DR14 to construct a sample of galaxy systems consisting of a
central object and two satellites. We adopt projected distance and radial
velocity difference criteria and impose an isolation criterion to avoid
membership in larger structures. We also classify the interaction between the
members of each system through a visual inspection of galaxy images, finding
$\sim80\%$ of the systems lack evidence of interactions whilst the remaining
$\sim20\%$ involve some kind of interaction, as inferred from their observed
distorted morphology. We have considered separately, samples of satellites and
central galaxies, and each of these samples were tested against suitable
control sets to analyse the results. We find that central galaxies showing
signs of interactions present evidence of enhanced star formation activity and
younger stellar populations. As a counterpart, satellite samples show these
galaxies presenting older stellar populations with a lower star formation rate
than the control sample. The observed trends correlate with the stellar mass
content of the galaxies and with the projected distance between the members
involved in the interaction. The most massive systems are less affected since
they show no star formation excess, possibly due to their more evolved stage
and less gas available to form new stars. Our results suggest that it is
arguable a transfer of material during interactions, with satellites acting as
donors to the central galaxy. As a consequence of the interactions, satellite
stellar population ages rapidly and new bursts of star formation may frequently
occur in the central galaxy.
