Speaker
Description
Given its proximity and dramatic dynamical history, the Magellanic Cloud system represents a unique laboratory for the study of not only interacting dwarf galaxies but the ongoing process of the formation of the Milky Way and its halo. Here we focus on one aspect of the complex, 3-body interaction — the dynamical perturbation of the Small Magellanic Cloud (SMC) by the Large Magellanic Cloud (LMC), and, very specifically, on potential tidal effects seen most recognizably on the side of the SMC closest to the LMC (the eastern side of the SMC), where previous studies have reported a greater line-of-sight depth compared to its western side. Using a combination of Gaia astrometry and SDSS-IV APOGEE-2 DR17 spectroscopic data — including precise radial velocities and multi-element chemical abundances — we explore the well-known distance bimodality on the eastern side of the SMC. Through a variety of means, including estimated stellar distances, proper motions, and radial velocities, we characterize the two populations in the bimodality and compare their properties with those of populations elsewhere in the SMC. For example, by analysis of the APOGEE chemical abundances, we find that, while all regions explored by APOGEE seem to show a single chemical enrichment history, the metallicity distribution function (MDF), of the “far” heliocentric distance stars on the eastern periphery of the SMC resembles that for the more metal-poor fields of the western periphery, whereas the MDF for the “near” stars on the eastern periphery resembles that for stars in the center of the SMC, most especially in having a metal-rich tail extending more metal rich than [Fe/H] = −0.85. The closer eastern periphery stars also show radial velocities (corrected for SMC rotation and bulk motion) that are, on average, approaching us relative to all other SMC populations sampled. We interpret these trends as evidence that the near stars on the eastern side of the SMC represent material pulled out of the central SMC as part of its tidal interaction with the LMC.
