The Stellar Dynamics and Mass of NGC 1316 Using the Radial Velocities of Planetary Nebulae

We present a study of the kinematics of the outer regions of the early-type galaxy NGC 1316, based on radial velocity measurements of 43 planetary nebulae as well as deep integrated light absorption line spectra. The smoothed velocity field of NGC 1316 indicates fast rotation at a distance of 16 kpc, possibly associated with an elongated feature orthogonal to the inner dust lanes. The mean square stellar velocity is approximately independent of radius, and the estimated total mass of the system is 2.9 × 1011 M☉ within a radius of 16 kpc, implying an integrated mass-to-light ratio of M/LB ≃ 8.