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Session 17 - Supernovae.
Display session, Monday, January 15
North Banquet Hall, Convention Center

[17.12] Cosmological Parameters from Type Ia Supernova Multicolor Light Curve Shapes

A. G. Riess, W. H. Press, R. P. Kirshner (CFA)

We present an empirical method that uses blue, visual, red, and infrared multicolor light curve shapes (MLCS) to estimate the luminosity, distance, and total line-of-sight absorption of Type Ia supernovae (SN Ia's). This method is first applied to a ``training set'' of eight SN Ia light curves with independent distance estimates to derive the correlation between the LCS and the luminosity. We employ a linear estimation algorithm of the type developed by Rybicki and Press. Some of the results are similar to those obtained by Hamuy et al. with the advantage that MLCS measures interstellar extinction and produces quantitative error estimates for the distance. The light curves for 20 SN Ia's (10 of which are from the CTIO/Calán Search) are used to determine the MLCS distances of these supernovae. The Hubble diagram constructed using these LCS distances has a remarkably small dispersion of \sigma_B,V,R=0.15 mag. We use the light curves of SN 1972E and SN 1981B and the Cepheid distance to NGC 5253 and NGC 4536 to derive 66 \pm 6 km s^-1 Mpc^-1 for the Hubble constant. We then measure the Local Group motion relative to these SN Ia's by analyzing the distribution on the sky of velocity residuals from a pure Hubble flow. The solution is consistent with the rest frame of the cosmic microwave background as determined by the COBE measurement of the dipole temperature anisotropy, and also with many plausible bulk flows expected to accompany observed density variations. It is inconsistent with the velocity observed by Lauer and Postman. We also find that the properties of dust in distant galaxies hosting SN Ia's are consistent with those of Galactic dust as measured by the interstellar extinction curve.

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