Stellar velocity profiles and line strengths out to four effective radii in the early-type galaxies NGC 3379 and 821 (original) (raw)

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 (R e ) 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 R e is dark. The measured absorption line-strengths reveal a radial gradient with constant slope out to 4 R e .