SNLS: Overview and High-z Spectroscopy D. Andrew Howell (Toronto) for the SNLS Collaboration (see: for full list) Abstract The Supernova Legacy Survey (SNLS) will discover and obtain g’r’i’z’ lightcurves for more than 600 SNe Ia (0.2<z<1.0) to differentiate between competing models for Dark Energy. As a part of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS), we use a rolling search strategy to discover and monitor SNe in four one degree fields over the course of five years. We fit the multicolor lightcurves of the candidates to determine which are likely SNe Ia and send them for follow-up spectroscopy to Keck, VLT, Gemini, and Magellan. Here we show the results form Gemini, where we send our highest redshift targets. Four fields… D4 D2 D1 …each 1° (a fraction of which is shown here)… …are searched for SNe… D3 …which are recorded in the database. Discovery SN Photo-z Photo-z 0.80 Spec-z Early photometry is fit with SN Ia lightcurves and the candidate’s type and redshift are estimated from the SN photometry. This is mainly used to screen out obvious Type II SNe and AGNs, and to determine the optimal time to observe the SN spectroscopically. SNe II, Ib/c AGN SNe Ia Example Gemini Spectra Selected Gemini SN Ia spectra. The agreement with local SN Ia templates suggests that SNe at high redshift have counterparts at low redshift, so evolution is not a serious concern. Spectroscopic ID Spectra are fit with a  2 matching program against a library of SNe templates. Template host galaxy light is also subtracted. Blue: GMOS data rebinned to 5Å after host galaxy template subtraction. Black: the best fit nearby SN template. Red: GMOS observations S-G smoothed. Target Follow-up Gemini N & S and VLT (10hr/mo. each) provide almost all spectroscopic follow-up for the main component of the SNLS. Due to its low overheads the VLT observes the most targets, while Gemini focuses on the higher redshift candidates. Magellan and Keck (~15 nights/yr): With other collaborators we carry out additional follow-up programs: Ellis: intensive study of z<0.5 SNe, SNe II; Freedman: Y and J-band imaging; Perlmutter/DEEP: supplemental identification when D3 cannot be observed by VLT. Primary Program Additional Science Survey Progress Cumulative SNe, to Apr. 2004: Despite the fact that much of 2003 was presurvey ramp-up time, we already have > 300 probable SNe and >70 SNe Ia. Projected in 5 years: Given recent improvements, 20% more area, a larger time allocation, and improved search efficiency, we expect to have at least 600 confirmed SNe Ia in 5 years, possibly many more.. Dark Energy: If the survey continues at the projected pace, we will be able to place the following constraints on w. 582 SNe used in simulation. Red is for fixed  M. Lightcurves Gemini Statistics 4 filters: SNe are observed in g’r’i’z’, allowing unprecedented measurement of reddening and SN intrinsic colors. Time sampling: SNe are observed every 2-3 rest frame days during dark and gray time. A typical run includes 10 observing blocks – 5 visits to each of two deep fields. Rolling search: Because we always observe the same fields, every visit brings new SN discoveries and adds points to existing lightcurves. SNe are often discovered within a few days of explosion. (5) Certain Ia (4) Probable Ia (3) Consistent with Ia (2) Unknown (1) Probably not a Ia (0) Certainly not a Ia Candidates observed with Gemini-N and S from Aug – Apr “Index” represents our degree of confidence that a candidate is a SN Ia from the spectrum.