Constraining the Hubble Constant with a Type II Supernova

Abstract

We plan to determine the Hubble constant (H_0) to {\lsim}10% by directlyinferring distances to a sample of Type II-P supernovae (SNe) in theHubble flow (cz ~ 9000 km/s), independent of any of the lower rungs onthe distance ladder. Measurements of cosmological parameters arecurrently limited by the precision of H_0. Continuing our program, wepropose to obtain multi- epoch photospheric-phase high signal-to-noiseratio optical spectroscopic observations with GMOS. We will perform adetailed quantitative spectroscopic non-LTE model atmosphere analysis,and infer the SN distance with a {\lsim}10% accuracy. In two recentpapers (Dessart {\amp} Hillier 2006; Dessart et al. 2008), we findexcellent agreement between direct distance measurements to three nearbyType II-P SNe and other distance estimates (Cepheid, SBF). Ultimately,to reduce the statistical uncertainty in the inferred H_0 value, we planto collect distances for three more SNe over as many semesters, alongwith a comparable number obtained at the VLT.