AAS 207th Meeting, 8-12 January 2006
Session 15 SNLS
Poster, Monday, 9:20am-7:00pm, January 9, 2006, Exhibit Hall

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[15.03] A Cosmological Hubble Diagram for Type II-P Supernovae

P. Nugent (LBNL), M. Sullivan (University of Toronto), R. Ellis, A. Gal-Yam, D. Leonard (Caltech), D. A. Howell (University of Toronto), SNLS Collaboration

Recent work by Hamuy et al. has presented an important correlation between the absolute brightnesses of Type IIP supernovae (SNe IIP) and the expansion velocities derived from the minimum of the Fe II 5169ÅP-Cygni feature observed during the middle of their plateau phases. Using this correlation and various methods to derive the extinction along the line of sight, a Hubble diagram can be constructed with a scatter of only ~0.3 magnitudes - implying a distance precision just below the level in regular use for Type Ia supernovae. Here we present two refinements to this method whose aim is to improve the practicality of measuring the distances of SNe IIP to cosmologically-interesting redshifts (z~0.4). Employing this new method along with Keck absorption line spectroscopy of 5 distant events from the Canada France Hawaii Supernova Legacy Survey we construct the first cosmological Hubble diagram for SNe~IIP whose scatter is 0.26 mag. We thereby demonstrate the feasibility of a test, with present facilities, of the cosmic acceleration independently of that derived from measures of Type Ia supernovae.

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