NOAO >   Observing Info >   Approved Programs >   2001A-0215

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Proposal Information for 2001A-0215


PI: Eric Peng, The Johns Hopkins University, ericpeng@pha.jhu.edu
Address: 3400 N. Charles Street, Baltimore, MD 21218, USA

CoI: Holland Ford, The Johns Hopkins University

Title: Globular Clusters, Stellar Dynamics, and Dark Mass in the Halo of NGC 5128 (Cen A)

Abstract: Elliptical galaxies constitute a large fraction of the stars and dark matter in the local universe, yet there is still much debate over how they may have formed. The properties of the globular cluster (GC) systems and the stellar kinematics of ellipticals are key constraints on their possible evolutionary mechanisms. Because most ellipticals are relatively distant (beyond 5 Mpc), spectroscopy of GCs is limited to the very brightest. Hence, few studies of GC systems focus on their kinematics, and fewer are able to study ellipticals beyond a few effective radii. NGC 5128 (Centaurus A) is the nearest giant elliptical galaxy (3.5 Mpc) and a recent merger, making it a prime candidate for a detailed photometric and \it kinematic study. Our ongoing planetary nebula (PN) survey in Cen A found that the outer regions were rapidly rotating, and has been effective in probing the stellar kinematics in the halo. In view of this, we have surveyed the halo of Cen A using Mosaic II to obtain \it UBVRI and [OIII] imaging. We have identified hundreds of spectroscopically accessible GC candidates within 50 kpc, and ~\!\!100 PNe at projected radii between 20 and 80 kpc, We propose to use Hydra to measure the radial velocities of both the PNe and the GCs. Our goals are to : 1) Create a catalog of confirmed GCs at r_proj\!<\!50 kpc, 2) Determine the net rotation and velocity dispersions of the metal-poor and metal-rich GCs, 3) Compare the kinematics of the GCs to the stars (PNe) at large radii, and 4) Determine the distribution of dark matter beyond 40 kpc. These observations, combined with the Mosaic imaging of Cen A, will comprise the bulk of the PI's Ph.D. dissertation.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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