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Home List of Titles The kinematics and dynamics of the globular clusters and planetary nebulae of NGC 5128
Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/37916
- The kinematics and dynamics of the globular clusters and planetary nebulae of NGC 5128
- Woodley, Kristin A.; Harris, William E.; Beasley, Michael A.; Peng, Eric W.; Bridges, Terry J.; Forbes, Duncan A.; Harris, Gretchen L. H.
- 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 ± 15 and 31 ± 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°, while beyond 5 kpc the rotation axis twists ~180°. The velocity dispersion displays a steady increase with galactocentric radius for both metallicity populations, with means of 111 ± 6 and 117 ± 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 ± 6 km s-1 and a rotation axis of 170° ± 5° 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 ± 0.2) × 1012 Modot 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 ± 0.5) × 1012 Modot 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).
- Publication type
- Journal article
- Research centre
- Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing
- Astronomical Journal, Vol. 134 (Aug 2007), p. 494-510
- Publication year
- cD; Elliptical galaxies; Galaxy dynamics; Galaxy kinematics; GCs; Globular clusters; ISM; Lenticular galaxies; NGC 5128; Planetary nebulae; Star clusters
- University of Chicago Press
- Publisher URL
- Copyright © 2007 The American Astronomical Society. All rights reserved.
- Peer reviewed