Gaseous Disks in Elliptical Galaxies

Extract

A powerful way to measure the mass distribution in elliptical galaxies is to study systems with a central disk of ionized gas. Such disks occur in a small fraction (perhaps 10–20%) of nearby ellipticals, and the gas is generally believed to have been accreted from outside the galaxy as the result of a merger or interaction. Once the gas disk has settled into a principal plane of the stellar figure, measurements of its orientation and kinematics set strong constraints on the shape and orientation of the galaxy and allow us to derive M/L as a function of radius. Indeed, the observations discussed here were made at the ESO/MPI 2.2-m telescope as part of our ESO KEY-PROGRAMME, in which we aim to determine the mass-to-light ratios of nearby elliptical galaxies and examine the evidence for dark matter.