Stellar Velocity Profiles and Line-Strengths out to Four Effective Radii in the Early-Type Galaxy NGC 3379

Abstract

We describe a new technique to measure stellar kinematics and line-strengths at large radii in nearby galaxies. Using the integral-field spectrograph SAURON as a 'photon-collector', we obtain spectra out to four effective radii (Re) in the early-type galaxy NGC 3379. By fitting orbit-based models to the extracted stellar velocity profile, we find that ~40% of the total mass within 5 Re is dark. The measured absorption line-strengths reveal a radial gradient with constant slope out to 4 Re.