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D. A. Howell, L. Wang, J. C. Wheeler (The University of Texas)
The distribution of high redshift Type Ia supernovae (SNe Ia) with respect to projected distance from the center of the host galaxy is studied, and compared to the distribution of local SNe. The distribution of high-z SNe Ia is found to be similar to the local sample of SNe Ia discovered with CCDs, but different than the sample discovered photographically. This is shown to be due to the Shaw effect. These results have implications for the use of SNe Ia to determine cosmological parameters if the local sample of supernovae used to calibrate the light curve decline relationships is drawn from a sample discovered photographically. A K--S test shows that the probability that the high redshift SNe of the Supernova Cosmology Project (http://www-supernova.lbl.gov) are drawn from the same distribution as the low redshift calibrators as Riess et al.\ (1998, AJ, 116, 1009) is 0.1%. This is a potential problem because photographically discovered SNe are preferentially discovered farther away from the galaxy nucleus, where SNe show a lower scatter in absolute magnitude. This raises questions about calibration SNe sampling the full range of parameters potentially present in high redshift SNe Ia. No evidence for evolutionary effects is seen.
The author(s) of this abstract have provided an email address for comments about the abstract: howell@astro.as.utexas.edu