Halo orbits in cosmological disk galaxies: tracers of formation history

Understand

We analyze the orbits of stars and dark matter particles in the halo of a disk galaxy formed in a cosmological hydrodynamical simulation.

• The halo is oblate within the inner ~20 kpc and triaxial beyond this radius.
• About 43% of orbits are short axis tubes - the rest belong to orbit families that characterize triaxial potentials (boxes, long-axis tubes and chaotic orbits), but their shapes are close to axisymmetric.
• We find no evidence that the self-consistent distribution function of the nearly oblate inner halo is comprised primarily of axisymmetric short-axis tube orbits.