The 3D structure of the Small Magellanic Cloud
  The 3D structure of the inner Small Magellanic Cloud (SMC) is investigated
using the red clump (RC) stars and the RR Lyrae stars (RRLS). The V and I pass
bands photometric data from the Optical Gravitational Lensing Experiment (OGLE
III) catalogue are used. The mean dereddened I${_0}$ magnitude and the
dispersion in the I${_0}$ magnitudes are used to estimate the relative
positions of different regions in the SMC and the line of sight (LOS) depth
across the SMC respectively. From the analysis of both the populations we found
that the north eastern part of the SMC is closer to us and the line of sight
depth across the SMC is large. The radial density profile of the RC stars
suggest that they are more likely to be distributed in a nearly spheroidal
system. An elongation along the NE-SW direction is seen in the distribution of
the RC stars. Based on these results the observed SMC is approximated as a
triaxial ellipsoidal galaxy. The parameters of the ellipsoid obtained using
both the populations are found to be similar. The above estimated parameters
depend on the data coverage of the SMC. Using the RRLS with equal coverage in
all the three axes (data within 3 degrees in X, Y and Z axes), we estimated an
axes ratio of 1:1.33:1.61 with an inclination, i = 2.6 deg and position angle
of the projection of the ellipsoid, \phi = 70.2 deg. Our tidal radius estimates
and the recent observational studies suggest that the full extent of the SMC in
the XY plane is of the order of the front to back distance estimated along the
line of sight. These results suggest that the structure of the SMC is
spheroidal or slightly ellipsoidal. We propose that the SMC experienced a
merger with another dwarf galaxy at ~ 4-5 Gyr ago, and the merger process was
completed in another 2-3 Gyr. This resulted in a spheroidal distribution
comprising of stars older than 2 Gyr.
