We investigate, using the modeling code SHAPE, the three-dimensional
structure of the bipolar Homunculus nebula surrounding Eta Carinae, as mapped
by new ESO VLT/X-Shooter observations of the H2 λ=2.12125 micron
emission line. Our results reveal for the first time important deviations from
the axisymmetric bipolar morphology: 1) circumpolar trenches in each lobe
positioned point-symmetrically from the center and 2) off-planar protrusions in
the equatorial region from each lobe at longitudinal (~55 degrees) and
latitudinal (10-20 degrees) distances from the projected apastron direction of
the binary orbit. The angular distance between the protrusions (~110 degrees)
is similar to the angular extent of each polar trench (~130 degrees) and nearly
equal to the opening angle of the wind-wind collision cavity (~110 degrees). As
in previous studies, we confirm a hole near the centre of each polar lobe and
no detectable near-IR H2 emission from the thin optical skirt seen prominently
in visible imagery. We conclude that the interaction between the outflows
and/or radiation from the central binary stars and their orientation in space
has had, and possibly still has, a strong influence on the Homunculus. This
implies that prevailing theoretical models of the Homunculus are incomplete as
most assume a single star origin that produces an axisymmetric nebula. We
discuss how the newly found features might be related to the Homunculus
ejection, the central binary and the interacting stellar winds. We also include
a 3D printable version of our Homunculus model.Comment: 14 pages, 7 color figures, 1 interactive 3D figure (Figure 5,
requires Adobe Reader), published in MNRAS. A 3D printable version of our
Homunculus model can be downloaded from
http://svs.gsfc.nasa.gov/vis/a010000/a011500/a011568/Eta_Car_Homunuculus_3D_model.zip
or from the 'Supporting Information' link in the electronic version of the
MNRAS articl