A new kinematic and dynamic study of the halo of the giant elliptical galaxy NGC 5128 is presented .
From a spectroscopically confirmed sample of 340 globular clusters and 780 planetary nebulae , the rotation amplitude , rotation axis , velocity dispersion , and total dynamical mass are determined for the halo of NGC 5128 .
The globular cluster kinematics were searched for both radial dependence and metallicity dependence by subdividing the globular cluster sample into 158 metal-rich ( [ Fe/H ] > -1.0 ) and 178 metal-poor ( [ Fe/H ] < -1.0 ) globular clusters .
Our results show that the kinematics of the metal-rich and metal-poor subpopulations are quite similar : over a projected radius of 0 - 50 kpc , the mean rotation amplitudes are 47 \pm 15 and 31 \pm 14 km s ^ { -1 } for the metal-rich and metal-poor populations , respectively .
There is a indication within 0 - 5 kpc that the metal-poor clusters have a lower rotation signal than in the outer regions of the galaxy .
The rotation axis shows an interesting twist at 5 kpc , agreeing with the zero-velocity curve presented by Peng and coworkers .
Within 5 kpc , both metal-rich and metal-poor populations have a rotation axis nearly parallel to the north-south direction , which is 0 ^ { o } , while beyond 5 kpc the rotation axis twists \sim 180 ^ { o } .
The velocity dispersion displays a steady increase with galactocentric radius for both metallicity populations , with means of 111 \pm 6 and 117 \pm 6 km s ^ { -1 } within a projected radius of 15 kpc for the metal-rich and metal-poor populations ; however , the outermost regions suffer from low number statistics and spatial biases .
The planetary nebula kinematics are slightly different .
Out to a projected radius of 90 kpc from the center of NGC 5128 , the planetary nebulae have a higher rotation amplitude of 76 \pm 6 km s ^ { -1 } , and a rotation axis of 170 \pm 5 ^ { o } east of north , with no significant radial deviation in either determined quantity .
The velocity dispersion decreases with galactocentric distance .
The total mass of NGC 5128 is found using the tracer mass estimator , described by Evans et al. , to determine the mass supported by internal random motions and the spherical component of the Jeans equation to determine the mass supported by rotation .
We find a total mass of 1.0 \pm 0.2 \times 10 ^ { 12 } M _ { \odot } from the planetary nebula data extending to a projected radius of 90 kpc .
The similar kinematics of the metal-rich and metal-poor globular clusters allow us to combine the two subpopulations to determine an independent estimate of the total mass , giving 1.3 \pm 0.5 \times 10 ^ { 12 } M _ { \odot } out to a projected radius of 50 kpc .
Lastly , we publish a new and homogeneous catalog of known globular clusters in NGC 5128 .
This catalog combines all previous definitive cluster identifications from radial velocity studies and HST imaging studies , as well as 80 new globular clusters with radial velocities from a study of M.A .
Beasley et al .
( in preparation ) .