Triaxial
Elliptical Galaxies
•So, are
ellipticals simple to understand dynamically? Not so
clear. We’re seeing a 2D
picture of a 3D object.
•
•In general, elliptical galaxies rotate too slowly for this to account for
the flattening observed. In other
words, their ratios of rotational to random kinetic energy is too low.
•
•If ellipticity
e were due to rotation (e.g., a pure oblate rotator with
an isotropic velocity distribution) then (Vrot/σ)iso ~ (e/(1-e))1/2.
Is it?
•