Presence of red giant population in the foreground stellar sub-structure
  of the Small Magellanic Cloud
  The eastern region of the Small Magellanic Cloud (SMC) is found to have a
foreground stellar sub-structure, which is identified as a distance bimodality
(12 kpc apart) in the previous studies using Red Clump (RC) stars.
Interestingly, studies of Red giant branch (RGB) stars in the eastern SMC
indicate a bimodal radial velocity (RV) distribution. In this study, we
investigate the connection between these two bimodal distributions to better
understand the nature and origin of the foreground stellar sub-structure in the
eastern SMC. We use the Gaia EDR3 astrometric data and archival RV data of RGB
stars for this study. We found a bimodal RV distribution of RGB stars
(separated by 35 - 45 km/s) in the eastern and south-western (SW) outer
regions. The observed proper motion values of the lower and higher RV RGB
components in the eastern regions are similar to those of the foreground and
main-body RC stars respectively. This suggests that the two RGB populations in
the eastern region are separated by a similar distance as those of the RC
stars, and the RGB stars in the lower RV component are part of the foreground
sub-structure. Based on the differences in the distance and RV of the two
components, we estimated an approximate time of formation of this sub-structure
as 307+/-65 Myr ago. This is comparable with the values predicted by
simulations for the recent epoch of tidal interaction between the Magellanic
Clouds. Comparison of the observed properties of RGB stars, in the outer SW
region, with N-body simulations shows that the higher RV component in the SW
region is at a farther distance than the main body, indicating the presence of
a stellar Counter-Bridge in the SW region of the SMC.
