NOAO >   Observing Info >   Approved Programs >   2006A-0436

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Proposal Information for 2006A-0436


PI: David Andersen, NRC Herzberg Institute of Astrophysics, david.andersen@nrc-cnrc.gc.ca
Address: 5071 West Saanich Rd, Victoria, BC V9E2E7, Canada

CoI: Rob Swaters, UMD
CoI: Matthew Bershady, UW-Madison
CoI: Marc Verheijen, University of Groningen
CoI: Kyle Westfall, UW-Madison

Title: The Distribution of Mass in Spiral Galaxies

Abstract: Little is known about the content and distribution of dark matter in spiral galaxies. Mass modeling of any rotation curve can yield an alarming range of results - from entirely halo-dominated, centrally- concentrated dark distributions, to disk-dominated inner potentials with shallow, low density halos. To break this degeneracy, we propose to take advantage of the unique properties of the SparsePak Integral Field Unit on WIYN. To do this successfully, a two-phased observational approach is required. We have completed the first phase, and obtained H(alpha) velocity fields for a sample of ~100 photometrically selected spiral galaxies. We now propose to continue the second phase, during which we will measure the stellar kinematics and velocity dispersions for a subsample of about 40 galaxies that the H(alpha) data show to have kinematically well behaved disks and suitable inclinations. The stellar velocity dispersions provide a kinematic measurement of the stellar disk mass, thus breaking the degeneracy, making possible a measurement of the dark matter properties in spiral galaxies with unprecedented accuracy. In addition, we will calibrate the stellar mass- to-light ratios (M/Ls) from population models (derived from our UBVRIJHK observations) by comparison to our dynamically determined M/Ls.


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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