Supernova Legacy Survey Mark Sullivan University of Oxford

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

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 Largest single telescope sample by survey end by survey end

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

First-Year SNLS Hubble Diagram SNLS 1 st year – 71 high-z SNe Ia Ω M = ± (stat) ± (sys) =-1.02 ± 0.09 (stat) ± (sys) (with BAO + Flat Universe) Astier et al citations (297 in refereed journals)

SNLS 3 rd year versus 1 st year Increase in SN numbers: 71 to ~250 Ability to test SN sub-samples (+ “astrophysical systematics”) 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 Deeper/more frequent z’ exposures increases utility of z>0.7 SNe 3-year monitoring of fields; better understanding of Megacam array 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 “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 0.16mag) New light curve fitting techniques exploit better understanding of SN light curves at λ 0.16mag)

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

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

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

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

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

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

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 Passive hosts Star-forming hosts

Colour correction required in all host types – with a similar β Either: a)Passive hosts have dust b)An intrinsic relation dominates over dust SN Colour (c) Residual without c-correction Passive hosts Star-forming hosts 40 high-z SNe 180 high-z SNe 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…

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

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

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 Howell et al Nearby z<0.75 z>0.75 Full 1 st year sample: solid s 1 at z>0.4: dashed

Future SN Ia Prospects Short-term: Current constraints on : =-1 to ~6-7% (stat) (inc. flat Universe, BAO+WMAP-3) At SNLS survey end statistical uncertainty will be 4-5%: 500 SNLS SDSS + larger local samples 500 SNLS SDSS + larger local samples Improved external constraints (BAO, WL) 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 Urgent need for z<0.1 samples with wide wavelength coverage Not clear what the “next step” at high-z should be Not clear what the “next step” at high-z should be

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