NOAO >   Observing Info >   Approved Programs >   2004B-0177

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Proposal Information for 2004B-0177


PI: Sheila Kannappan, University of Texas at Austin, sheila@astro.as.utexas.edu
Address: McDonald Observatory, 1 University Station, C1402, Austin, TX 78712-0259, USA

CoI: Matthew Bershady, University of Wisconsin at Madison
CoI: Elizabeth Barton, University of Arizona

Title: Kinematic Tully-Fisher Offsets at z=0 and Beyond

Abstract: Interpreting apparent evolution in the Tully-Fisher (TF) relation relies on knowing whether shifts in slope and zero point reflect offsets in luminosity or offsets in rotation velocity. In fact, the ``differential luminosity evolution'' claimed in many high-redshift TF studies looks disturbingly similar to the pattern of offsets seen for low-z galaxies with strongly asymmetric or truncated rotation curves. The low-z outliers are probably subject to both luminosity and velocity offsets. Their velocity shifts may arise not just from rotation curve abnormalities but also from symmetric kinematic distortions and errors in parameters that affect velocity measurements (P.A. and inclination). To calibrate these effects, we have begun collecting 2D H(alpha) velocity fields for a sample of known low-z TF outliers and a control sample. We will use the 2D data to model distortions and establish accurate rotation velocities, and also to determine kinematic inclinations and position angles. By comparing the 2D results with standard TF parameters we can measure the kinematic contributions to TF offsets. To apply our results to higher z, we will degrade the images and spectroscopy, using the 2D H(alpha) fields to model slit aperture effects. We will also search for ways to estimate kinematic offsets from other galaxy properties in the absence of 2D velocity fields. This program was originally granted long-term status to assemble a broad sample spanning all the relevant parameters. Due to poor weather and instrumental overhead, we have observed just over half the original sample. To complete the survey we request renewed long-term status, with 1 night in 2004B and 2 in 2005A.


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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