Three dimensional maps of the Magellanic Clouds using RR Lyrae Stars and
  Cepheids II. The Small Magellanic Cloud
  We use data on variable stars from the Optical Gravitational Lensing
Experiment (OGLE III) survey to determine the three-dimensional structure of
the Small Magellanic Cloud (SMC). Deriving individual distances to RR Lyrae
stars and Cepheids we investigate the distribution of these tracers of the old
and young population in the SMC. Photometrically estimated metallicities are
used to determine the distances to 1494 RR Lyrae stars, which have typical ages
greater than 9 Gyr. For 2522 Cepheids, with ages of a few tens to a few hundred
Myr, distances are calculated using their period-luminosity relation.
Individual reddening estimates from the intrinsic color of each star are used
to obtain high precision three-dimensional maps. The distances of RR Lyrae
stars and Cepheids are in very good agreement with each other. The median
distance of the RR Lyrae stars is found to be 61.5 +/- 3.4 kpc. For the
Cepheids a median distance of 63.1 +/- 3.0 kpc is obtained. Both populations
show an extended scale height, with 2.0 +/- 0.4 kpc for the RR Lyrae stars and
2.7 +/- 0.3 kpc for the Cepheids. This confirms the large depth of the SMC
suggested by a number of earlier studies. The young population is very
differently oriented than the old stars. While we find an inclination angle of
7{\deg} +/- 15{\deg} and a position angle of 83{\deg} +/- 21{\deg} for the RR
Lyrae stars, for the Cepheids an inclination of 74{\deg} +/- 9{\deg} and a
position angle of 66{\deg} +/- 15{\deg} is obtained. The RR Lyrae stars show a
fairly homogeneous distribution, while the Cepheids follow roughly the
distribution of the bar with their northeastern part being closer to us than
the southwestern part of the bar. Interactions between the SMC, LMC, and Milky
Way are presumably responsible for the tilted, elongated structure of the young
population of the SMC.
