Dark matter in early-type galaxies: a SAURON view

Anne-Marie Weijmans (Leiden Observatory)

From galaxy formation theory we expect galaxies to be embedded in massive dark matter haloes. For spiral and dwarf galaxies this has indeed been observationally confirmed, by modeling the kinematics from the large cold gas discs that often surround these galaxies. These gas discs are however rare in elliptical galaxies, to that we have to resort to other tracers when we want to probe their dark matter haloes, which are not always easily accessible. As a result, dark haloes for only a handful of early-type galaxies have been mapped.

In this talk I will give an overview of the methods that can be used to find dark matter in early-type galaxies. I will then focus on two projects that I worked on with the integral-field spectrograph SAURON, using two different methods to constrain the dark halo. The first is based on the combination of two-dimensional ionised gas and cold gas kinematics. The second method uses SAURON as a 'photon collector', to
obtain spectra at large radii in galaxies. From these spectra we can not only obtain the velocity profile and construct mass models to discuss some future prospects.