NOAO >   Observing Info >   Approved Programs >   2002A-0315

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Proposal Information for 2002A-0315


PI: Stephane Courteau, Univ. of British Columbia, courteau@astro.ubc.ca
Address: 6224 Agricultural Rd., Vancouver, BC V6T 1Z1, Canada

CoI: Matthew Bershady, Univ. of Wisconsin
CoI: Hans-Walter Rix, MPIA, Heidelberg
CoI: David Andersen, MPIA, Heidelberg

Title: A Critical Test of Structure Formation Models

Abstract: We seek to constrain current models of structure formation and the hypothesis of maximal disks in luminous spiral galaxies. Structure formation models based on most CDM cosmologies favor dark galactic halos that dominate the potential even in the inner parts of galaxies. Opposite conclusions are reached if the rotation curve of galaxies can only be modeled with the highest (maximal) disk mass-to-light ratio. Stellar population and Tully-Fisher (TF) analyses of low and high surface brightness galaxies suggest a picture where dark matter concentration correlates with surface brightness. Since bright barred galaxies have typically higher surface brightness than their un-barred cousins, they should have different halo concentrations and thus should define their own separate TF sequence. This clear prediction cannot be tested at present since barred galaxies have systematically been excised from TF samples in the past. We propose to augment our own TF Shellflow sample with 24 barred galaxies to test this claim. Whether barred galaxies define a brighter TF sequence or they behave dynamically as un- barred galaxies, in a TF sense, is of utmost importance for structure formation models. Fiber spectroscopy with WIYN/SparsePak is required to model the full 2D velocity fields of the bulge, bar, and disk components. Disk scale lengths, magnitudes, and colors are measured from 0.9m deep V-I photometry.


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NOAO >   Observing Info >   Approved Programs >   2002A-0315

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