OGLE-ing the Magellanic System: Stellar populations in the Magellanic
  Bridge
  We report the discovery of a young stellar bridge, that forms a continuous
connection between the Magellanic Clouds. This finding is based on number
density maps for stellar populations found in data gathered by OGLE-IV, that
fully cover over 270 deg^2 of the sky in the Magellanic Bridge area. This is
the most extensive optical survey of this region up to date. We find that the
young population is present mainly in the western half of the MBR, which,
together with the newly discovered young population in the eastern Bridge, form
a continuous stream of stars connecting both galaxies along Dec ~ -73.5 deg.
The young population distribution is clumped, with one of the major densities
close to the SMC, and the other, fairly isolated and located approximately
mid-way between the Clouds, which we call the OGLE island. These overdensities
are well matched by HI surface density contours, although the newly found young
population in the eastern Bridge is offset by ~2 deg north from the highest HI
density contour. We observe a continuity of red clump stars between the
Magellanic Clouds, which represent an intermediate-age population. Red clump
stars are present mainly in the southern and central parts of the Magellanic
Bridge, below its gaseous part, and their presence is reflected by a strong
deviation from the radial density profiles of the two galaxies. This may
indicate either a tidal stream of stars, or that the stellar halos of the two
galaxies overlap. On the other hand, we do not observe such an overlap within
an intermediate-age population represented by the top of the red giant branch
and the asymptotic giant branch stars. We also see only minor mixing of the old
populations of the Clouds in the southern part of the Bridge, represented by
the lowest part of the red giant branch.
