UVIT Study of the MAgellanic Clouds (U-SMAC) II. A Far-UV catalog of the Small Magellanic Cloud: Morphology and Kinematics of young stellar population

TL;DR

This study presents a far-UV catalog of nearly 77,000 sources in the Small Magellanic Cloud, analyzing the morphology and kinematics of young stellar populations to understand the galaxy's recent interaction history.

Contribution

It provides the first comprehensive far-UV catalog of the SMC and investigates the morphology and kinematic properties of its young stellar populations.

Findings

Detected a clumpy morphology with broken bar and shell-like structures.

Identified two kinematically distinct sub-populations among young stars.

Found kinematic disturbances aligned with the galaxy's interaction history.

Abstract

The Small Magellanic Cloud (SMC) is an irregular dwarf galaxy that has recently undergone an interaction with the Large Magellanic Cloud. The young massive stars in the SMC formed in the disturbed low-metallicity environment are important targets in astrophysics. We present a catalog of $\sim$ 76,800 far ultraviolet (FUV) sources towards the SMC detected using the Ultra Violet Imaging Telescope (UVIT) onboard AstroSat. We created an FUV catalog with $\sim$ 62900 probable SMC members which predominantly comprise main-sequence, giant, and subgiant stars. We selected 4 young populations (Young 1, Young 2, Young 3, and Blue Loop (BL) stars) identified from the Gaia optical color-magnitude diagram to study the morphology and kinematics of the young SMC using this catalog. We detect a clumpy morphology with a broken bar, a shell-like structure, and the inner SMC Wing for the 4 stellar populations. The eastern region and the northeastern regions are mainly populated by Young 1, 2, and 3. The central region predominantly has the Young 2 and 3 populations, whereas the SW has BL stars, Young 2 and 3. The 2-D kinematic study using proper motion (PM) reveals that Young 2 and 3 populations show two kinematically distinct sub-populations with low and high PM dispersion, whereas the Young 1 and BL stars show two kinematically distinct populations with low dispersion. Our analysis points to a kinematic disturbance along the RA direction for stars younger than $\sim$ 150 Myr located in the eastern region, with no significant disturbance along the Declination.