Poster Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

Outer triaxiality of a ‘Fast Rotator’ (#222)

Caroline Foster 1
  1. Australian Astronomical Observatory, North Ryde, NSW, Australia

As part of their pioneering work, the ATLAS3D team have shown that several morphologically elliptical galaxies are centrally kinematically disky. Hence, while global morphology suggests that ellipticals are ellipsoidal/triaxial in shape, their central kinematics are more consistent with (inclined) oblate systems.

We obtain galaxy light kinematics of the centrally kinematically disky elliptical NGC 4473 out to 2.5 effective radii. While we confirm previous results in the central regions, we find that at large galactocentric radii NGC 4473 exhibits an interesting kinematic transition. In the outskirts, we observe clear minor and major axis rotation, a tell-tale sign of triaxiality. Hence, we conclude that the stellar halo of NGC 4473 is consistent with being triaxial as also inferred from its Hubble type.

We conclude that NGC 4473 is centrally axisymmetric with an important transition into an outer ‘kinematically decoupled halo’ (KDH), in agreement with theoretical expectations.