Bridge over troubled gas : clusters and associations under the SMC and LMC tidal stresses

Abstract

We obtained Southern Astrophysical Research telescope B and V photometry of 14 star clusters and two associations in the Bridge tidal structure connecting the Large and Small Magellanic Cloud (LMC and SMC). These objects are used to study the formation and evolution of star clusters and associations under tidal stresses from the Clouds. Typical star clusters in the Bridge are not richly populated and have in general relatively large diameters (≈30–35 pc), being larger than Galactic counterparts of similar age. Ages and other fundamental parameters are determined with field-star decontaminated photometry. A self-consistent approach is used to derive parameters for the most-populated sample cluster NGC 796 and two young CMD templates built with the remaining Bridge clusters. We find that the clusters are not coeval in the Bridge. They range from approximately a few Myr (still related to optical H II regions and WISE and Spitzer dust emission measurements) to about 100–200 Myr. The derived distance moduli for the Bridge objects (1h56m < α < 2h28m) suggests that the Bridge is a structure connecting the LMC farside in the east to the foreground of the SMC to the west. Most of the present clusters are part of the tidal dwarf candidate D 1, which is associated with an H I overdensity.We find further evidence that the studied part of the Bridge is evolving into a tidal dwarf galaxy, decoupling from the Bridge.