Kinematic complexity around NGC 419: resolving the proper motion of the cluster, the Small Magellanic Cloud, and the Magellanic bridge

ABSTRACT We present Hubble Space Telescope proper motions in the direction of the star cluster NGC 419 in the Small Magellanic Cloud. Because of the high precision of our measurements, for the first time it is possible to resolve the complex kinematics of the stellar populations located in the field, even along the tangential direction. In fact, the proper motions we measured allow us to separate cluster stars, which move on average with ($\mu _{\alpha }\cos \delta ^{\rm NGC\, 419}, \mu _{\delta }^{\rm NGC\, 419}$) = (+0.878 ± 0.055, −1.246 ± 0.048) mas yr−1, from those of the Small Magellanic Cloud and those belonging to a third kinematic feature that we recognize as part of the Magellanic Bridge. Resolving such a kinematic complexity enables the construction of decontaminated colour–magnitude diagrams, as well as the measurement of the absolute proper motion of the three separate components. Our study therefore sets the first steps towards the possibility of dynamically investigating the Magellanic system by exploiting the resolved kinematics of its stellar clusters.

OGLE-ing the Magellanic System: Three-Dimensional Structure

We present a three-dimensional structure of the Magellanic System using over 9 000 Classical Cepheids and almost 23 000 RR Lyrae stars from the OGLE Collection of Variable Stars. Given the vast coverage of the OGLE-IV data and very high completeness of the sample, we were able to study the Magellanic System in great details.We very carefully studied the distribution of both types of pulsators in the Magellanic Bridge area. We show that there is no evident physical connection between the Clouds in RR Lyrae stars distribution. We only see the two extended structures overlapping. There are few classical Cepheids in the Magellanic Bridge area that seem to form a genuine connection between the Clouds. Their on-sky locations match very well young stars and neutral hydrogen density contours. We also present three-dimensional distribution of classical pulsators in both Magellanic Clouds.