Detection, photometry and slitless radial velocities of 535 planetary 
nebulae in the flattened elliptical galaxy NGC 4697

Roberto H. Mendez 
Munich University Observatory, Germany

This talk will describe the first large-scale experience of slitless
radial velocity measurements of planetary nebulae (PNs) in an elliptical
galaxy. The observations were made with the ESO Very Large Telescope.
The radial velocity information is obtained from PN positions in direct
images and slitless grism images. The measurement and calibration 
procedures will be explained. Velocities can be obtained for all detected 
PNs in the field, irrespective of their number and distribution, with 
errors below 40 km/s. Photometry of the PNs permits to build their 
luminosity function, from which an accurate distance can be derived. 
The PN radial velocities provide kinematic information up to a distance 
of almost 3 effective radii from the nucleus; the rotation curve and 
line-of-sight velocity dispersion profile can be used to constrain the 
mass-to-light ratio and dark matter content in NGC 4697.