2007ApJ...664..257D

We present results from Planetary Nebula Spectrograph (PN.S) observations of the elliptical galaxy NGC 3379 and a description of the data reduction pipeline. We detected 214 planetary nebulae, of which 191 are ascribed to NGC 3379 and 23 to the companion galaxy NGC 3384. Comparison with data from the literature shows that the PN.S velocities have an internal error of ≲20 km.s^–1 and a possible offset of similar magnitude. We present the results of kinematic modeling and show that the PN kinematics is consistent with absorption-line data in the region where they overlap. The resulting combined kinematic data set, running from the center of NGC 3379 out to more than 7 effective radii (R_eff), reveals a mean rotation velocity that is small compared to the random velocities and a dispersion profile that declines rapidly with radius. From a series of Jeans dynamical models we find the B-band mass-to-light ratio inside 5R_eff to be 8-12 in solar units, and the dark matter fraction inside this radius to be less than 40%. We compare these and other results of dynamical analysis with those of dark matter-dominated merger simulations, finding that significant discrepancies remain, reiterating the question of whether NGC 3379 has the kind of dark matter halo that the current ΛCDM paradigm requires.