Gemini Spectroscopic Survey of Young Star Clusters in
  Merging/Interacting Galaxies. IV. Stephan's Quintet
  We present a spectroscopic survey of 21 young massive clusters and complexes
and one tidal dwarf galaxy candidate (TDG) in Stephan's Quintet, an interacting
compact group of galaxies. All of the selected targets lie outside the main
galaxies of the system and are associated with tidal debris. We find clusters
with ages between a few and 125 Myr and confirm the ages estimated through HST
photometry by Fedotov et al. (2011), as well as their modelled interaction
history of the Quintet. Many of the clusters are found to be relatively
long-lived, given their spectrosopically derived ages, while their high masses
suggest that they will likely evolve to eventually become intergalactic
clusters. One cluster, T118, is particularly interesting, given its age (\sim
125 Myr), high mass (\sim 2\times10^6 M\odot) and position in the extreme outer
end of the young tidal tail. This cluster appears to be quite extended (Reff
\sim 12 - 15 pc) compared to clusters observed in galaxy disks (Reff \sim 3 - 4
pc), which confirms an effect we previously found in the tidal tails of NGC
3256, where clusters are similarly extended. We find that star and cluster
formation can proceed at a continuous pace for at least \sim 150 Myr within the
tidal debris of interacting galaxies. The spectrum of the TDG candidate is
dominated by a young population (\sim 7 Myr), and assuming a single age for the
entire region, has a mass of at least 10^6 M\odot.
