Discovery and photometric follow-up at CFHT

1. SNLS - THE SUPERNOVA LEGACY SURVEY P. Astier (LPNHE, Paris), E. Aubourg (CEA, Saclay), D. Balam (U. Victoria), C. Balland (LPNHE, Paris), S. Basa (LAM, Marseille), R. Carlberg (U. Toronto), I. Hook (U. Oxford), D. Guide (LPNHE, Paris), Julien Guy (LPNHE, Paris), D. Hardin (LPNHE, Paris), A. Howell (U. Toronto), R. Knop (U. Vanderbilt), H. Lafoux (CEA, Saclay), T. Merrall (U. Toronto), A. Mourao (Centra, Lisbon), R. Pain (LPNHE, Paris), N. Palanques-Delabrouille (CEA, Saclay), S. Perlmutter (LBNL), K. Perrett (U. Toronto), C. Pritchet (U. Victoria), G. Sainton (LPNHE, Paris), M. Sullivan (U. Toronto), J. Raux (LPNHE, Paris), J. Rich (CEA, Saclay) http:// www.cfht.hawaii.edu/SNLS The SNLS has been allocated large amount of spectroscopic follow-up time at the VLT, Gemini North and South, Keck and Magellan. Example of a spectrum of a SN Ia at z=0.866 Observed at Gemini. Exposure 4800s, Seeing 0.5”, Nod-and-shuffle mode. First Results About 130 SN candidates have been found so far with 35 identified as SN Ia during a pre-survey which took place between April and August 2003. The survey is now running 60 % of the full rate with a plan to go 100 % in semester 2004A. Distribution of discovery, peak and spectroscopy magnitudes of supernova candidates found during the pre-survey. Achievable precision This five year survey will yield a Hubble diagram with about 1000 SN Ia measured with an unprecedented precision. A direct and precise measurement of the cosmological parameters, WM and WL, will be performedand will provide a measurement of the cosmic equation of state. Discovery and photometric follow-up at CFHT Discovery and photometric follow-up of supernovæ is performed in a so called “Rolling Search” mode by continuous sampling of the same fields. Four square degrees are surveyed for 5 six months periods with 1h i’-filter exposure every 2-3 night. The fields are observed every 2-3 nights in g’, r’ and z’ as well. Several hundred of Type Ia and Type II and Ib/c supernovæ will be detected and precisely followed-up. To precisely measure the SN Ia luminosity at maximum, a S/N of about 10 is required during a time interval roughly 10 days before and after the peak luminosity. Measurement of the color excess E(B-V) of the supernovæ is needed to address extinction. For redshifts up to z=0.8, this is achieved with i-filter exposures (r-filter exposures for redshifts up to z=0.6). For higher redshifts, measurements in z-filter and/or IR will be required. Alternatively E(U-B) could be used if a good description of the SN Ia variability in u-filter is available. Preliminary analysis of a z=0.866 SN Ia r’- and i’-filter light curves observed during the September and October 2003 runs. Spectroscopic identification Identification of supernova types and redshift determination of the host galaxy rely on spectroscopy.Spectral identification of SN Ia can be achieved in about one hour on an 8-m class telescope up to redshifts z0.9. • Type Ia Supernovae for Cosmology • Type Ia supernovae (SN Ia) peak luminosity dispersion can be reduced to about 0.15 magnitude using a luminosity-decline rate relation. • About 5 years ago, the Supernova Cosmology Project and the High-Z Supernova team reported evidence for a non zero cosmological term using SN Ia as “calibrated” candles. • The next step is to achieve precise measurement of the cosmological parameters WM and WL and to measure the equation of state of Dark Energy, pDE=w.rDE. • Measurements of supernovae rates as a function of redshift are also of great interest to constrain the Star Formation Rate. • These goals can be achieved by collecting sample of about a thousand of well measured high redshift supernovae • A “Rolling Search” Survey mode • Supernova surveys are usually done in three steps: • Detection by subtracting images of the same field taken two consecutive new moons apart. • Spectroscopic identification from supernova spectroscopy at or near maximum light and redshift determination from host galaxy spectral features. • Light curve photometry by subtracting the underlying host galaxy light. • Since August 2003, the SuperNova Legacy Survey project (SNLS) has engaged in a new high redshift supernova survey using the newly commissioned 1 square degree wide field imager MegaPrime, a joint project of CFHT and CEA/DAPNIA. • SNLS is part of the CFHT Legacy Survey program, a large multi purpose imaging survey that will take place at CFHT over the next five years. SNLS will use 202 nights of observations over 5 years.