Dark Energy in the Supernova Legacy Survey Mark Sullivan (University of Toronto)

Toronto Group Ray Carlberg, Mark Sullivan, Andy Howell, Kathy Perrett, Alex Conley French Group Reynald Pain (PI), Pierre Astier, Julien Guy, Nicolas Regnault, Jim Rich, Stephane Basa, Dominique Fouchez UK Gemini PI: Isobel Hook Victoria Group Chris Pritchet, Don Neill, Dave Balam USA LBL: Saul Perlmutter CIT: Richard Ellis Plus: Many students and associate members throughout the world

AAS Calgary June 2006 SNLS: Vital Statistics 202n/5 year rolling SN survey Uses “Megacam” 36CCD 1 sq. deg. imager on the CFHT Observe in griz every 4 th night in Grey/Dark time Typical seeing: arcsec Depth i’>24.5 (S/N=8) in 1 hr 4 survey fields; 2 always available: Queue scheduling – and the highest queue priority – offers protection from weather D1 (02:26,-04) VIMOS, SWIRE, GALEX, XMM Deep D2 (10:00,+02) COSMOS: ACS, Spitzer, GALEX, XMM etc. D3 (14:19,+53) Groth Strip: – ACS, DEEP-II, GALEX etc. D4 (22:15,-18) GALEX, XMM Deep

AAS Calgary June 2006 Organisation CFHT-LS (imaging) – DEEPWIDE Galaxy studies Time sequenced dataset (202n over 5 years) Cosmic shear Clusters SNLS collaboration Data-processing Major Spectroscopic Program Gemini (Canada/UK/USA) 120 hrs/yr (60:40:20) VLT (France/Other Euros) 120 hrs/yr Keck (through LBL) 40 hrs/yr Cosmological analyses Magellan near-IR study (Freedman et al.) Rest-frame I-band Hubble diagram Keck SN Ia UV study (Ellis/Sullivan et al.) LRIS high-S/N - metallicity through UV lines Testing accuracy of k-corrections in the UV SN IIP study (Nugent/Sullivan/Ellis et al.) Using SNe IIP as standard candles Independent Hubble diagram to z=0.5

AAS Calgary June 2006 Current Status Survey has now been running for 3 years Nearly 300 spectroscopically confirmed SNe Ia “On track” for 500 by survey end “On track” for 500 by survey end

AAS Calgary June 2006 Rolling Light-curves

AAS Calgary June 2006 Redshift distribution Redshift range: 0.08<z<1.06

SNLS-03D4ag

AAS Calgary June 2006 Typical light-curves z = 0.91 z = 0.36 Rolling search: Lightcurves are equally well-sampled at all phases

AAS Calgary June 2006 Cosmological Constraints

AAS Calgary June 2006 First-Year SNLS Hubble Diagram First Year Results (Astier et al. 2006) Intrinsic disp.: 0.13 ± 0.02 Low-z: 0.15 ±0.02 SNLS: 0.12 ± 0.02 Assuming flatness, w=-1: Ω M = ± 0.042

AAS Calgary June 2006 Dark energy: SNLS + BAO Assuming flatness: Ω M = ± w= ± 0.087

AAS Calgary June 2006 Dark energy: SNLS + WMAP Spergel et al. (2006)

AAS Calgary June 2006 Coming soon… The first year SNLS dataset provides the best SN sample for measuring “w” This sample is only 10-15% of the final sample Third Year cosmological analysis: Data collection complete in 2 months Data collection complete in 2 months SN sample 4-5 times larger SN sample 4-5 times larger Improved “z” data will make the higher-redshift SNe more cosmologically powerful than in Year 1 Improved “z” data will make the higher-redshift SNe more cosmologically powerful than in Year 1 Results should be ready in the Fall Results should be ready in the Fall

AAS Calgary June 2006 Where Next?

AAS Calgary June 2006 Current status – and where next? First year: N~70; w=-1.02 N~70; w=-1.02 w: ±0.09 (stat) (RED) w: ±0.09 (stat) (RED) w: ±0.055 (sys) (BLUE) w: ±0.055 (sys) (BLUE) Third Year: N~ N~ End-of-survey: N~ N~ ±~0.05 (stat) ±~0.05 (stat) ±??? (sys) ±??? (sys) Substantial effort needs to be invested not only in “N”, but in reducing systematics

AAS Calgary June 2006 Potential Systematics in measuring w Photometric zeropoints Mismatches to local SNe observations Mismatches to local SNe observations Contamination by non-SNe Ia Spectroscopy is critical Spectroscopy is criticalK-corrections U and near-UV uncertain - see poster by Eric Hsiao U and near-UV uncertain - see poster by Eric HsiaoExtinction Effective R B ; Dust evolution; Grey dust Effective R B ; Dust evolution; Grey dust Redshift evolution in the mix of SNe “Population drift” “Population drift” Evolution in SN properties Light-curves/Colors/Luminosities Light-curves/Colors/Luminosities More “mundane” More “scientifically interesting”

? White Dwarf Many competing models for: Nature of progenitor system – the “second star” Nature of progenitor system – the “second star” Single versus double degenerate Single versus double degenerate Young versus old progenitor Young versus old progenitor Explosion mechanism? Explosion mechanism? Mass transfer mechanism? Mass transfer mechanism?

AAS Calgary June 2006 SNLS work on understanding SNe Ia Relationship with environment (Sullivan et al. 2006) SN explode in galaxies with different ages/metallicities SN explode in galaxies with different ages/metallicities Population “drift”? – galaxy mix evolves with redshift Population “drift”? – galaxy mix evolves with redshift Evolution in SN properties Rise-time analysis (Conley et al. 2006) Rise-time analysis (Conley et al. 2006) High signal/noise UV spectroscopy (Ellis/Sullivan et al.) Progenitor metallicity mostly affects the UV – Evolution? Progenitor metallicity mostly affects the UV – Evolution? Improved U-band k-corrections Improved U-band k-corrections Relationship with environment (Sullivan et al. 2006) SN explode in galaxies with different ages/metallicities SN explode in galaxies with different ages/metallicities Population “drift”? – galaxy mix evolves with redshift Population “drift”? – galaxy mix evolves with redshift Evolution in SN properties Rise-time analysis (Conley et al. 2006) Rise-time analysis (Conley et al. 2006) High signal/noise UV spectroscopy (Ellis/Sullivan et al.) Progenitor metallicity mostly affects the UV – Evolution? Progenitor metallicity mostly affects the UV – Evolution? Improved U-band k-corrections Improved U-band k-corrections

AAS Calgary June 2006 Evolution in Ia properties with z? Riess et al rise time of low-z and high-z SNe different by 5.8 . Limitations: Inhomogeneous data No early-time data Conley et al. find low-z and high-z SNLS risetimes consistent at 1  Conley et al. 2006, AJ, submitted t r : rise time

AAS Calgary June 2006 PassivePassive Star-formingStar-forming StarburstingStarbursting  CFHT u*g’r’i’z’ imaging via the Legacy program. (UofT seeing limit stacks)  PEGASE2 is used to fit SED templates to the optical data.  Recent star-formation rate, and total stellar mass are estimated.  Sources classified based on their specific star-formation rate.  CFHT u*g’r’i’z’ imaging via the Legacy program. (UofT seeing limit stacks)  PEGASE2 is used to fit SED templates to the optical data.  Recent star-formation rate, and total stellar mass are estimated.  Sources classified based on their specific star-formation rate. Optical Typing of SNe Ia hosts

AAS Calgary June 2006 SNLS: SN rate as a function of sSFR Use specific star- formation rate (SFR per unit mass) to classify the SNLS SNIa hosts Per unit stellar mass, SNe are at least an order of magnitude more common in more vigorously star- forming galaxies SNLS “passive” galaxies 125 Host Galaxies at z<0.75 Low-redshift data from Mannucci et al. 2005

AAS Calgary June 2006 “A+B” Model Scannapieco & Bildsten (2005) and Mannucci et al. (2005): Two component model Prompt: t=0 and P=0 at all other times Delayed: P=A constant with time

AAS Calgary June 2006 Mannucci et al – P(t) “Delayed”“Prompt” “A+B” essentially approximates the details of the SNIa delay-time probability distribution

AAS Calgary June 2006 Mix will evolve with redshift… Relative mix evolves strongly with redshift “B” component “A” component “A+B” total Neill et al. (2006) SNLS SNIa rate

AAS Calgary June 2006 Light-curve width / host-type Light-curve width is a key parameter for standardizing SNe Ia as calibrateable candles We use the “stretch” technique (e.g. Perlmutter et al. 1997) Stretch is known to depend on environment locally: e.g. Riess et al. (1999), Hamuy et al. (1995;2000) e.g. Riess et al. (1999), Hamuy et al. (1995;2000)

AAS Calgary June 2006 Stretch/Environment Stretch  Fainter SNe Brighter SNe 

AAS Calgary June 2006 Further evidence for A+B? All star-forming galaxies Star-forming galaxies plus “mass-scaled” passive All star-forming galaxies MINUS passive

AAS Calgary June 2006 Other environmental differences? (Conley et al. 2006, AJ submitted) No evidence for gross differences between light- curves in passive and active galaxies

AAS Calgary June 2006 Cosmological effects? “First-year” SNLS dataset plus low-z classified by morphology More to come in the third year analyses… Black – passive Red – active

AAS Calgary June 2006 Spectral UV evolution studies Possible metallicity clues in the far-UV spectrum Address concerns over systematics? Address concerns over systematics? Little is known in the UV at z=0 Atmosphere precludes observations Atmosphere precludes observations Space-based time is hard to come by Space-based time is hard to come by Try at intermediate redshift – where a guaranteed supply of SNe (SNLS) removes scheduling problems Keck-I/LRIS campaign (PI: Ellis) using LRIS-B ~25 high-quality (S/N) spectra down to rest-frame 2800A Lentz et al. (2000) Varying metallicity changes line blanketing in the UV

AAS Calgary June 2006 Mean z=0.5 UV spectrum Ellis, Sullivan et al. Preliminary

AAS Calgary June 2006 Summary SNLS is a mature survey – 8-10 new SNe Ia confirmed every month With nearly 300 SNe Ia in hand, the survey will have around 500 by the scheduled finish in st year SNLS dataset is the most uniform, well understood, and statistically powerful SN Ia data set SNLS data is currently the best SN Ia dataset to combine with either BAO or WMAP data to measure dark energy.

AAS Calgary June 2006 Summary The challenge now is the control of systematics: SNe Ia know and “care” about their environment SNe Ia know and “care” about their environment Light-curve width depends on age of the progenitor population Light-curve width depends on age of the progenitor population Evidence for wide-range of delay-times, or two progenitors – relative mix evolves with redshift? Evidence for wide-range of delay-times, or two progenitors – relative mix evolves with redshift? The final SNLS data set will be essential for constraining systematics for next generation projects like the LSST or NASA’s JDEM.

AAS Calgary June 2006 Publications! Cosmology: Astier et al. (2006), A&A 447, 31 SN Ia Rates: Neill et al. (2006), AJ in press Host galaxy connection: Sullivan et al. (2006), ApJ in press SN Ia Risetimes: Conley et al. (2006), AJ submitted SN selection and screening: Sullivan et al. (2006), AJ 113, 960 SN Spectroscopy: Howell et al. (2005), ApJ 634, 1190 SNII-P Hubble Diagram: Nugent et al. (2006), ApJ in press

AAS Calgary June 2006 SNLS – The Next Generation SNLS-I will conclude some time in 2008 SNLS-II is now under discussion: ? ? Little spectroscopy? Use photometric typing techniques developed by SNLS-I Little spectroscopy? Use photometric typing techniques developed by SNLS-I All detections/light-curves publicly available All detections/light-curves publicly available Lower redshift (z=0.6), >5x wider area – g’r’i’ only Lower redshift (z=0.6), >5x wider area – g’r’i’ only Improved control of systematics Improved control of systematics

AAS Calgary June 2006 SNLS: Host Galaxy properties Spectral template fitting: PEGASE-2 photometric redshift code takes galaxy spectral templates, and fits them to observed magnitudes (ugriz fluxes) As we know the redshift, we keep this fixed u g r i z SNLS-03D1au z=0.51 The evolutionary models give us the parameters that define the galaxy SED e.g. Integrated stellar mass,Integrated stellar mass, Average recent star-formation historyAverage recent star-formation history

AAS Calgary June 2006 Two component model – SFR SNIa Rate by host SFR Subtracting off the passive component in star-forming galaxies reveals that the SNIa rate is consistent with being linearly proportional to SFR Fitting all galaxies simultaneously gives slopes of: N mass =1.02 ± 0.10 N SFR =0.98 ± 0.11 Log (Galaxy SFR) 

AAS Calgary June 2006 Two component model – Mass SNIa Rate by host mass The SNIa rate is linearly proportional to host stellar mass in galaxies with no star-formation Star-forming galaxies show an excess of SNe Ia at lower masses Log (stellar mass) 

AAS Calgary June 2006 Supernova Legacy Survey Keck (8 nights/yr) Gemini N & S (120 hr/yr) VLT (120 hr/yr) Magellan (15 nights/yr) Imaging CFHT Legacy Survey Deep program Spectroscopy Types, redshifts from 8m-class telescopes DiscoveriesLightcurves g’r’i’z’ every 4 days during dark time