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B. Catinella (NAIC and Cornell U.), M.P. Haynes, R. Giovanelli (Cornell U.)
The determination of the rotational parameters of disk galaxies is of crucial importance for several areas of observational cosmology, including studies of galaxy formation and evolution over cosmic time. N-body simulations of cosmological scenarios suggest that disk scaling relations such as the Tully-Fisher (TF) relation should change as galaxies evolve. Recent studies based on optical spectroscopy of modest numbers of spiral galaxies have reached conflicting conclusions on the possible evolution of the mass-to-light ratio. The Sloan Digital Sky Survey (SDSS) promises to provide a huge, homogeneous data base of linewidths for galaxies with an average redshift z~0.11, some 30% of which might be useful for applications of the TF relation after restrictions for galaxy morphology, inclination and isolation are imposed. Because the SDSS fiber technique generally does not sample the full extent of a galaxy rotation curve (RC), SDSS linewidths provide a measurement of rotational velocity that depends on the redshift of the galaxy, on the physical size of its line-emitting region, and on the intrinsic shape of its RC. For TF applications therefore, the SDSS linewidths must be corrected for their "aperture bias", at least in a statistical sense.
We used our large sample of ~3000 low redshift galaxies with I-band photometry and long-slit optical spectroscopy to study the average properties of their RCs (namely, shape and extent) in different luminosity intervals. Using these results, we have simulated the effects of the fixed aperture on extracted linewidths for galaxies with realistic RCs in the redshift range covered by the SDSS spectroscopic sample, and have derived statistical corrections to be applied to those linewidths as a function of redshift and luminosity.
This work is partially funded by NSF grants AST-9900695 and AST-0307396.
The author(s) of this abstract have provided an email address for comments about the abstract: bcatinel@naic.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.