The Standard Candle Method for Type II-Plateau Supernovae

TL;DR

This study refines the standard candle method for Type II-Plateau supernovae, achieving a 12-14% distance measurement precision and an H_0 estimate consistent with other methods, by analyzing photometry and spectroscopy of 37 supernovae.

Contribution

It introduces an analytic procedure for fitting supernova light, color, and velocity curves, and determines the host-galaxy reddening and R_V value to improve distance estimates.

Findings

Achieved a distance precision of 12-14%.

Derived a R_V value of 1.4 +/- 0.1.

Obtained H_0 = 70 +/- 8 km/s/Mpc.

Abstract

In this thesis we study the "standardized candle method" using a sample of 37 nearby (redshift < 0.06) Type II-plateau supernovae with BVRI photometry and optical spectroscopy. An analytic procedure is implemented to fit light, color, and velocity curves. We find that the V-I color toward the end of the plateau can be used to estimate host-galaxy reddening with a precision of 0.2 mag. The luminosity-expansion velocity relation previously reported in the literature is recovered. Using this relation and assuming a standard reddening law (R_V = 3.1), we obtain Hubble diagrams in the BVI bands with approximate dispersions of 0.4 mag. Allowing R_V to vary and minimizing the spread in the Hubble diagrams, we obtain a dispersion of 0.25-0.30 mag, which implies that these objects can deliver distances with a precision of 12-14 %. The resulting value of R_V is 1.4 +/- 0.1. Using two supernovae with known Cepheid host-galaxy distances, we obtain H_0 = 70 +/- 8 km/s/Mpc, in very good agreement with the average value obtained with other modern, reliable methods.