The Occurrence/Non-occurrence of Dark Matter in Elliptical Galaxies

Wednesday, 02 December 2015 1 p.m. — 2 p.m. MST

AURA Lecture Hall

NOIRLab South Colloquia
TOM RICHTLER (Universidad de Concepción and Gemini South Visiting Astronomer)

While dark matter is an indispensable ingredient in standard theories of cosmological structure formation, the direct evidence for  dark matter through the dynamics of galaxies leads to confusion. The flat rotation curves of spiral galaxies can hardly be understood without dark matter, if one wants to avoid  modifying gravity. The situation for elliptical galaxies is more complicated because of the missing disk symmetry. One has to analyse the integrated light projected along an extended line of sight and for larger radii has to rely on dynamical tracers like globular clusters and planetary nebulae.


I summarize our present knowledge of dark matter in elliptical galaxies in various environments from central cluster galaxies  to isolated ellipticals. There is evidence that the MONDian phenomenology of galaxy dynamics also extends to elliptical galaxies. I introduce in some detail our programme of investigating isolated elliptical galaxies and present first results which are difficult to reconcile with the standard theory of  galaxy formation in dark matter halos.