Title: The Nature of Dark Energy from Type Ia Supernovae
Abstract: Type Ia supernovae (SNe Ia) currently provide the most direct evidence for an accelerating Universe and for the existence of an unknown "dark energy" driving this expansion. The 5-year Supernova Legacy Survey (SNLS) will deliver a definitive dataset with well-sampled g'r'i'z' light curves, allowing precise measurement of the cosmological parameters (Omega_Matter, Omega_Lambda). Based on our successful first year results (Astier et al., submitted) we expect the final sample to determine the cosmological equation of state parameter "w" to a statistical precision of +/-0.05, testing theories for the origin of the universal acceleration. The amount of spectroscopic follow-up performed will define the success of this survey. Approximately 700 of the 1000 SNe Ia detected will be spectroscopically confirmed in a coherent program involving all of the world's major telescopes (Gemini, VLT, Keck). Gemini, with nod-and-shuffle observations, plays a pivotal role within this collaboration (Howell et al. 2005). The goal for Gemini this semester is to obtain types and redshifts for 30 SN Ia candidates between redshift 0.6-0.9, contributing to a large, high quality and homogeneous SN Ia sample with photometry, spectroscopy, light-curve sampling, and colour information superior to any existing - or planned - sample. This is a continuing QR (quick response) proposal for GMOS-N.
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