UVIT Study of the MAgellanic Clouds (U-SMAC) I. Recent Star Formation History and Kinematics of the Shell Region in the North-Eastern Small Magellanic Cloud

The interactions between the Magellanic Clouds significantly affect the shapeand distribution of the young stellar population, particularly in the peripheryof the Small Magellanic Cloud (SMC). We present the first far-UV (FUV) map ofthe north-east SMC-Shell region using the Ultra Violet Imaging Telescope (UVIT)onboard AstroSat. The detected FUV stars are combined with Gaia Early DataRelease 3 data to create a FUV-optical catalog of   14,400 stars. FUV-opticalcolour-magnitude diagrams are used along with isochrones to estimate thestellar ages. The detected stars are formed in multiple episodes. We identifiedtwo episodes of star formation (  60 and   260 Myr ago) where the episode at  260 Myr is linked to the recent interaction with the Large Magellanic Cloud(LMC) and the episode at   60 Myr is linked to the pericentric passage of theSMC around our Galaxy. The median proper motion (PM) and velocity dispersionare found to be similar to the SMC main body, indicating that this region hasnot experienced significant tidal effects. The FUV stellar surface density andthe dispersion in PM suggest an extent of the inner SMC in the north-eastdirection to be around 2.2 deg. We detect arm-like and arc-like structures inthe FUV stellar density map, and their kinematics appear to be similar to theSMC main body. These extended outer features are the spatial stellaroverdensities formed over multiple episodes of star formation, but withoutapparent kinematic distinction.