SNLS: Overview and High-z SpectroscopySNLS: Overview and High-z SpectroscopyD. Andrew Howell (Toronto) for the SNLS Collaboration (see: D. Andrew Howell (Toronto) for the SNLS Collaboration (see: http://cfht.hawaii.edu/SNLS 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.

DiscoveryDiscovery

SN Photo-zSN Photo-z

Photo-z 0.80

Spec-z 0.843

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

AGNSNe Ia

Example Gemini SpectraExample Gemini SpectraSelected 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 IDSpectroscopic 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-upTarget 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 ProgressSurvey ProgressCumulative 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.

LightcurvesLightcurves

Ib/c7%

II11%

Unknown26%

Ia56%

Gemini StatisticsGemini 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.

Name Old Name Date Exptime z Type Index03D4cj c030821-02 8/26/2003 3600 0.27 Ia 503D4ck c030821-03 8/27/2003 2400 0.189 IIn 003D4cn c030821-06 8/27/2003 4800 0.818 Ia? 303D1as c030918-12 9/27/2003 6000 0.872 ? 103D1ax c030918-17 9/29/2003 2400 0.496 Ia 503D1bk c030922-04 9/28/2003 4800 0.865 Ia 503D4cy c030903-02 9/26/2003 5400 0.927 Ia 403D4cz c030903-03 9/27/2003 3600 0.695 Ia 403D1cj c031021-01 10/26/2003 5400 0.364 Ib/c? 103D1cm c031021-04 10/27/2003 5400 0.87 Ia? 303D1co c031021-06 11/1/2003 4800 0.68 Ia 403D4fd c031017-01 10/24/2003 3600 0.791 Ia 503D4fe c031017-02 10/24/2003 3600 ? ? 203D4gl c031022-02 10/29/2003 3600 0.56 Ia 403D1ew c031217-01 12/21/2003 7200 0.868 Ia 503D1fp c031219-04 12/26/2003 7200 0.27 IIb 003D1fq c031219-05 12/24/2003 5400 0.81 Ia? 304D3aa c040113-01 1/30/2004 5400 0.205 II 004D3ae c040113-05 1/25/2004 2400 0.217 II 004D3ax c040119-03 1/28/2004 5400 0.356 ? 104D3dd c040414-02 4/24/2004 5400 1.01 Ia 404D3de c040414-04 4/26/2004 7200 ? ? 204D3fj c040421-01 4/27/2004 5400 ? ? 204D3fq c040421-03 4/25/2004 5400 0.73 Ia? 404D2aa c040117-01 1/23/2004 7320 0.549 ? 204D2ad c040117-04 1/22/2004 7320 0.68 ? 204D2ae c040117-05 1/21/2004 5490 0.843 Ia 5

(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. 2003 – Apr. 2004. “Index” represents our degree of confidence that a candidate is a SN Ia from the spectrum.