The Halo Dynamics of NGC 3379: A Normal Elliptical Galaxy with No Dark Matter

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Session 6 -- Normal Galaxies: Structure and Dynamics
Display presentation, Monday, 9:20-6:30, Pauley Room

[6.19] The Halo Dynamics of NGC 3379: A Normal Elliptical Galaxy with No Dark Matter

R. Ciardullo (Penn State), G.H. Jacoby (KPNO)

We present the results of a radial velocity survey of planetary nebulae in the normal, non-interacting, elliptical galaxy NGC~3379. In two half-nights with the Kitt Peak 4-m telescope and the NESSIE multifiber spectrograph, we measured the velocities of 29~PNe with projected galactocentric distances between 0.4 and 3.8 effective radii (1~kpc $< R <$~10 kpc). These data, which have an observational uncertainty of $\sim 7$~km~s$^{-1}$, extend 3 times further into the halo than any previous absorption line study, and allow us for the first time, to examine the kinematics of halo stars in a normal E0 galaxy.

The observed velocity dispersion and photometric profile of NGC 3379 agrees extremely well with that expected from a constant mass-to-light, isotropic orbit Jaffe model with a mass-to-light ratio $M/L_B \sim 7$. A simple $c = 2.33$ King model with $M/L_B \sim 7$ also fits the data reasonably well, but models with purely radial or circular orbits are ruled out. The data strongly suggest that NGC~3379 is a galaxy with little or no dark matter within 3.5 effective radii of its nucleus.

Monday program listing