Lodovico Coccato (ESO)

Title 
The kinematics of early-type galaxy halos probed by Planetary Nebulae.

Abstract
Stellar halos offer an unique laboratory to study the assembly of the
barions and dark matter in early-type galaxies. Indeed, the dynamic
time scales at those large radii are few Gyr, and the imprint of the
formation process may still be preserved in the halo properties:
kinematics, orbital structure, and stellar populations.

Unlike spirals, the kinematics and mass content of early-type galaxy
halos is difficult to measure, due to the lack of neutral or ionized
gas. Planetary Nebulae, because of their bright OIII emission line at
5007 angstrom, can be detected far out several effective radii in the
stellar halo. They can be used as test particles to unveil the
kinematic properties of the halo, derive the mass distribution, probe
the presence of substructures and the relics of recent merger events.

The Planetary Nebulae Spectrograph mounted at the WHT in La Palma
(Spain) is a dedicated instrument to detect and measure the velocity
of planetary nebulae in nearby galaxies. I will overview the results
and the challenges of its observational campaign.