Gemini spectroscopic survey of young star clusters in merging/interacting galaxies. I. NGC 3256 tidal tail clusters

We present Gemini optical spectroscopy of three young star clusters in the western tidal tail of NGC 3256. Compact star clusters (as opposed to dwarf galaxy candidates) in tidal tails are rare, and these three clusters are the first for which detailed quantitative spectroscopy has ever been obtained. We find that two of these clusters appear to be coeval, while the third is approximately 2 times older (similar to 200Myr vs. similar to 80 Myr). All three clusters are massive (1-3 x 10(5) M(circle dot)) and appear to be of roughly solar metallicity. In addition, the three clusters appear to be relatively large (R(eff)=10-20 pc), possibly reflecting weak compression at the time of formation and/or the weak influence of the tidal field of the galaxy. All three clusters have velocities consistent with the general trend of the H (I) velocities in the tidal tail. We conclude that if the loosely bound tail material of NGC 3256 gets stripped during future interactions of this galaxy within its group, these three clusters may become part of the intragroup medium.