The most distant compact groups
  We present photometric and spectroscopic observations of the members of three
previously cataloged compact group (CG) candidates at redshifts z>0.3. These
confirm spectroscopic redshifts compatible with being gravitationally bound
structures at redshifts 0.3112, 0.3848 and 0.3643 respectively, and then they
are the most distant CGs known with spectroscopic confirmation for all their
members. The morphological and spectroscopic properties of all their galaxies
indicate early types dominated by an old population of stars, with little star
formation or nuclear activity. Most of the physical properties derived for the
three groups are quite similar to the average properties of CGs at lower
redshifts. In particular, from the velocities and positions of the respective
members of each CG, we estimate short dynamic times. These leave open the
questions of identifying the mechanism for forming CGs continuously and the
nature of the final stages of these structures.
