A Robust Measure of Dark Matter Halo Ellipticities
  In simulations of the standard cosmological model (LCDM), dark matter halos
are aspherical. However, so far the asphericity of an individual galaxy's halo
has never been robustly established. We use the Jeans equations to define a
quantity which robustly characterizes a deviation from rotational symmetry.
This quantity is essentially the gravitational torque and it roughly provides
the ellipticity projected along the line of sight. We show that the Thirty
Meter Telescope (TMT), with a single epoch of observations combined with those
of the Gaia space telescope, can distinguish the LCDM value of the torque from
zero for each Sculptor-like dwarf galaxy with a confidence between 0 and 5
sigma, depending on the orientation of each halo. With two epochs of
observations, TMT will achieve a 5 sigma discovery of torque and so asphericity
for most such galaxies, and so will provide a new and powerful test of the LCDM
model.
