The expanding photosphere method (EPM): distance calculations to 12 Type II-P Supernovae and a comparison with the Standard Candle Method

Title from first page of PDF file (viewed January 7, 2011)Includes bibliographical references (p. 69-73)The use of independent methods to calculate extragalactic distances is important to help constrain cosmological parameters and to provide mutual checks on the external accuracy of other distance measuring techniques. In this thesis we present EPM distance estimates to 12 nearby (???150 Mpc) Type II-Plateau Supernovae (SNe II-P) that are drawn from a sample for which distances have previously been determined using the Standardized Candle Method (SCM), an independent distance-measuring technique for SNe II-P. We use the same photometric and spectral data as was used in the SCM study, which enables a direct comparison between the two techniques. To calculate our EPM distances we employ the filter subsets {BV} , {BVI} and {VI}. Our "best" EPM distance estimates are derived as the mean of the three individual distances. Comparing the EPM and SCM measurements, we find a systematic offset of 11:9 ?? 5:2%, in the sense that EPM distances are larger. This offset is significantly less than that found by a similar recent study using a different dataset. We speculate on potential causes of the discrepancy between the two studies. Finally, using our "best" EPM distance estimates, we derive a Hubble constant of H??? = 81:4 ?? 10:0 (statistical) km/s/Mpc