Supernova Legacy Survey

1. Supernova Legacy Survey Mark Sullivan University of Oxford http://legacy.astro.utoronto.ca/ http://cfht.hawaii.edu/SNLS/

2. USA LBL: Saul Perlmutter, + … Paris Group Reynald Pain, Pierre Astier, Julien Guy, Nicolas Regnault, Christophe Balland, Delphine Hardin, Jim Rich, + … Toronto Group Ray Carlberg, Alex Conley, Andy Howell, Kathy Perrett Victoria Group Chris Pritchet, Dave Balam, + … Marseille Group Stephane Basa, Dominique Fouchez Oxford Isobel Hook (Gemini PI), Mark Sullivan, Emma Walker The SNLS collaboration Full list of collaborators at: http://cfht.hawaii.edu/SNLS/

3. SNLS: Vital Statistics • 5 year “rolling” SN survey • Goal: 500 high-z SNe to measure “w” • Uses “Megacam” imager on the CFHT; griz every 4 nights in queue scheduled mode • Survey running for 4 years • ~350 confirmed z>0.1 SNe Ia • >1500 SN detections in total • Largest single telescope sample • 450-500 by survey end

4. “Measured” maximum light magnitude “c” – B-V colour estimator corrects for extinction and/or intrinsic variation via β s – “stretch” corrects for light-curve shape via α Standard absolute B-band magnitude Cosmology with SNe Ia • Distance estimator constructed in rest-frame B-band: Note: for the cosmological fits is >>1 unless an “intrinsic dispersion” term is added – this parameterises our lack of knowledge about SNe

5. First-Year SNLS Hubble Diagram SNLS 1st year – 71 high-z SNe Ia Astier et al. 2006 470 citations (297 in refereed journals) ΩM = 0.263 ± 0.042 (stat) ± 0.032 (sys) <w>=-1.02 ± 0.09 (stat) ± 0.054 (sys) (with BAO + Flat Universe)

6. SNLS 3rd year versus 1st year • Increase in SN numbers: 71 to ~250 • Ability to test SN sub-samples (+ “astrophysical systematics”) • Optimised survey design and calibration • Deeper/more frequent z’ exposures increases utility of z>0.7 SNe • 3-year monitoring of fields; better understanding of Megacam array • Improved understanding of SN Ia properties • New “k-correction” template (Hsiao et al. 2007) incorporates Ellis et al. UV spectra: reduction in potential source of systematics • New light curve fitting techniques exploit better understanding of SN light curves at λ<4000A (rms: 0.19 -> 0.16mag)

7. Hubble Diagram ~240 distant SNe Ia (error was 0.042 in A06) Sullivan et al. in prep

8. Cosmological Constraints (Preliminary) SNe WMAP-3 6-7% measure of <w> SNe BAO BAO SNLS+BAO (No flatness) SNLS + BAO + simple WMAP + Flat (relaxing flatness: error in <w> goes from ~0.065 to ~0.115)

9. Potential SN Systematics in measuring w(a) • “Experimental Systematics” • Calibration, photometry, Malmquist-type effects • Contamination by other SNe or peculiar SNe Ia • Minimized by spectroscopic confirmation • Non-SNe systematics • Peculiar velocities; Hubble Bubble; Weak lensing • K-corrections and SN spectra • UV uncertain; “golden” redshifts; spectral evolution? • Extinction/Colour • Effective RV;Intrinsic colour versus dust • Redshift evolution in the mix of SNe • “Population drift” – environment? • Evolution in SN properties • Light-curves/Colors/Luminosities “Extinction” Increasing knowledge of SN physics “Population Evolution”

10. Colour correction β=4.1 Colour—luminosity relationship inconsistent with MW-type dust Best-fit: β~3 MW-dust: β≡RB=4.1 Residual without c-correction SN Colour (c)

11. SN colour-colour space In colour colour space, MW-type extinction laws also don’t work SN B-V SN U-B

12. Combination of dust+intrinsic? In colour colour space, MW-type extinction laws also don’t work SN B-V SN U-B

13. Residuals by host type • SNe in passive galaxies show a smaller scatter • “Intrinsic dispersion” consistent with zero (Does intrinsic dispersion in SNe arise from dust?) • Cleaner sample: But SNe in passive galaxies are at high-z (~20%: two component model) + very few locally Star-forming hosts Passive hosts

14. 180 high-z SNe Colour correction required in all host types – with a similar β Either: • Passive hosts have dust • An intrinsic relation dominates over dust Residual without c-correction Star-forming hosts Large “local” SN surveys covering a wide wavelength range (inc. near-IR) urgently needed to disentangle this Not clear what more of the same will tell us… 40 high-z SNe Residual without c-correction Passive hosts SN Colour (c)

15. SN Ia SFR dependencies – potential evolution? SN rate versus host SFR SN stretch distributions split by galaxy star-formation rate SN Ia rate per unit mass Star-forming hosts SFR per unit mass Passive hosts 170 SNLS SNe Ia (Update from Sullivan et al. 2006; better zeropoints, host photometry, more SNe) SN stretch (s)

16. SN mix predicted to evolve with redshift Predicted mix of two components evolves strongly with redshift

17. Nearby z<0.75 z>0.75 Redshift drift in stretch? Average stretch, and thus average intrinsic brightness of SNe Ia evolves with redshift if stretch correction works perfectly, this will not affect cosmology Full 1st year sample: solid s<1 at z<0.4 and s>1 at z>0.4: dashed Howell et al. 2007

18. Future SN Ia Prospects Short-term: • Current constraints on <w>: <w>=-1 to ~6-7% (stat) (inc. flat Universe, BAO+WMAP-3) • At SNLS survey end statistical uncertainty will be 4-5%: • 500 SNLS + 200 SDSS + larger local samples • Improved external constraints (BAO, WL) Longer term: • No evolutionary bias in cosmology detected (tests continue!) • SNe in passive galaxies: seem more powerful probes, but substantially rarer (esp. at high-z) • Colour corrections are the dominant uncertainty • Urgent need for z<0.1 samples with wide wavelength coverage • Not clear what the “next step” at high-z should be

19. USA LBL: Saul Perlmutter, + … Paris Group Reynald Pain, Pierre Astier, Julien Guy, Nicolas Regnault, Christophe Balland, Delphine Hardin, Jim Rich, + … Toronto Group Ray Carlberg, Alex Conley, Andy Howell, Kathy Perrett Victoria Group Chris Pritchet, Dave Balam, + … Marseille Group Stephane Basa, Dominique Fouchez Oxford Isobel Hook (Gemini PI), Mark Sullivan, Emma Walker The SNLS collaboration Full list of collaborators at: http://cfht.hawaii.edu/SNLS/