1. www.astro.uvic.ca/~pritchet The Supernova Legacy Survey (SNLS): New Results on Cosmology and the Nature of Type Ia Supernovae

2. www.astro.uvic.ca/~pritchet Toronto Group Ray Carlberg, Mark Sullivan, Andy Howell, Kathy Perrett, Alex Conley French Group Reynald Pain, Pierre Astier, Julien Guy, Nicolas Regnault, Jim Rich, Stephane Basa, Dominique Fouchez UK Gemini PI: Isobel Hook + Justin Bronder, Richard McMahon, Nic Walton Victoria Group Chris Pritchet, (Don Neill), Dave Balam, Eric Hsiao, Melissa Graham USA LBL: Saul Perlmutter CIT: Richard Ellis Plus: Many students and associate members throughout the world

3. www.astro.uvic.ca/~pritchet Special Mention … Andy Howell – PDF U.Toronto Melissa Graham U Victoria Alex Conley – PDF U Toronto Eric Hsiao U Victoria Mark Sullivan – PDF U Toronto Kathy Perrett – PDF U Toronto, Ms. Data Dave Balam, RA, U Victoria

4. www.astro.uvic.ca/~pritchet  Historical Background  Supernova Cosmology  SNLS Overview  SNLS Results  Other SN Science  Conclusions/Future

5. www.astro.uvic.ca/~pritchet Golden Moments in Cosmology repulsive force repulsive force, vacuum energy, ρ=const ρ=const “Much later, when I was discussing cosmological problems with Einstein, he remarked that the introduction of the cosmological term was the biggest blunder of his life.” – G. Gamow, “My World Line” (1970)

6. www.astro.uvic.ca/~pritchet Hubble Diagram (ℓ vs z) faintbright nearby distant V [km/s] Assumptions: Inverse square law ℓ =L/4πd² Euclidean space Standard candle (what Hubble actually did to demonstrate the expansion of the Universe)

7. www.astro.uvic.ca/~pritchet Hubble Diagram and Cosmology log d or log z log apparent brightness Ω=1 Ω<1 Ω>1 Curvature of space causes deviations from linear Hubble diagram. Ω<1 means expansion forever. Standard candle! High ρ Low ρ z = v/c = Δλ/λ 1+z = R o /Rflat

8. www.astro.uvic.ca/~pritchet Hubble 1953 Cosmology – A Search for 2 Numbers? H o – rate of expansion (v=H o d) Ω o – deceleration - matter density

9. www.astro.uvic.ca/~pritchet Gunn and Oke 1975 “… although the heterogeneity of the sample makes conclusions about cosmology slightly suspect.” -2 < Ω <0 +2 < Ω < +4 Kristian, Sandage and Westphal 1978 >400 nights of Palomar 200” time! evolution (mass and age)

10. www.astro.uvic.ca/~pritchet  Historical Background  Supernova Cosmology  SNLS Overview  SNLS Results  Other SN Science  Conclusions/Future

11. www.astro.uvic.ca/~pritchet SNe Ia vs SNe II – a Primer SN Ia SN Ia SN II SN II brightness 10 10 L sun ~10 9 L sun progenitor 1 or 2 white dwarfs (M>1.4Msun) massive star mechanism mass transfer or merger; thermonuclear disruption core collapse progenitor age ~10 10 yr~10 7 yr evolution with z Little?(1+z) 2-4 :

12. www.astro.uvic.ca/~pritchet Making a standard candle Phillips 1993

13. www.astro.uvic.ca/~pritchet More 56 Ni  Higher Temp  Higher Opacities  Brighter, Broader SNe Ia Higher opacities trap the radiation more effectively and release it later, making for broader light curves. (Nugent) (But Kasen & Woosley astro-ph/ 0609540) s= stretch Log L Making a standard candle Peak brightness is a std candle. σ~ 0.15 mag

14. www.astro.uvic.ca/~pritchet Making a standard candle

15. www.astro.uvic.ca/~pritchet Supernovae as Cosmological Probes  Max brightness makes an excellent standard candle - ±6% distance errors  Bright - can be seen to cosmological distances  Standard candle has a physical basis SNeIa are “well-understood” - thermonuclear disruptions of C+O white dwarfs - std physics  “The supernova distance-redshift relation comes from the FRW metric. That’s it. Issues of DE sound speed, anisotropic stress, matter growth, etc, do not affect this probe.” (Linder 2006)  Systematics – possibly, but ample opportunity to study with potentially hundreds of objects

16. www.astro.uvic.ca/~pritchet Supernovae and Dark Energy Not:  i/s abs (hi z)  evolution  selection effects Riess et al. 1998 Perlmutter et al. 1999 Cosmological constant Λ Universe is accel- erating. Λ exists!

17. www.astro.uvic.ca/~pritchet Dark Energy - a Strange Brew …  Expansion is accelerating  Vacuum energy,  Vacuum energy, ρ ≈ const Einstein was right!  Ω tot =Ω M +Ω DE =1  ρ Λ ≈ 10 -8 eV cm -3 ≈ 10 -120 x “theoretical value”  ρ Λ ≈ ρ M – why??

18. www.astro.uvic.ca/~pritchet “On a good day I can think of 3 or 4 plausible candidates for dark matter. The same cannot be said for dark energy.” “On a good day I can think of 3 or 4 plausible candidates for dark matter. The same cannot be said for dark energy.” - Rocky Kolb, Tucson, Mar 2004 “Our theoretical understanding is so limited right now …” - Rocky Kolb, Tucson, Mar 2004 “… DE is not understood sufficiently to answer the basic questions …” - Rocky Kolb, Tucson, Mar 2004 Rocky Horror Show – Tucson 2004

19. www.astro.uvic.ca/~pritchet What is the Dark Energy? What is it ?? Copeland et al astro-ph/ 0603057

20. www.astro.uvic.ca/~pritchet What is the DE?  Cosmological Constant Λ  Pure vacuum energy  Some other new physical component  e.g. scalar field models, quintessence, Chaplygin gas models  A new physical law  e.g. modifications to GR What is it ?? “Raffiniert is der Herrgott, aber boshaft ist er nicht.” (Einstein) (Einstein’s translation: “God is slick, but he ain’t mean.”)

21. www.astro.uvic.ca/~pritchet Equation of State Parameter “w” P = w  ρ(a) ~ a -3(1+w) w = 1/3 radiation w = 0 matter w > -1 “quintessence” w = -1 Λ  w is a measurable.  most sensitivity at z<1.  w,dw/dz constrain DE.

22. www.astro.uvic.ca/~pritchet  Background  Supernova Cosmology  SNLS Overview  SNLS  Other SN Science  Conclusions

23. www.astro.uvic.ca/~pritchet MegaCam at CFHT  Built by CEA  1 deg x 1 deg field  40 x (2048 x 4612) chips ~ 400Megapixels  good blue response “Size matters …” Anon.

24. www.astro.uvic.ca/~pritchet CFHT Legacy Survey  SNLS - Deep (“SNe + galaxy evolution”)  4 deg², long time sequenced exposures  202 nights  Wide (“weak lensing”)  172 deg² in 3 patches  Very Wide (“KBO”)  1300 deg², +-2 deg from ecliptic,  short exposures 470 nights (dark-grey) over 5 years (2003-2008) Hoekstra et al 2006 astro-ph/0511089

25. www.astro.uvic.ca/~pritchet  202 nights over 5 years  202 nights over 5 years (part of CFHTLS)  four 1 deg² fields  queue scheduled obs, 3-4 day temporal sampling  griz filters (450-950nm)  spectroscopic followup (VLT, Gemini, Keck, Magellan)  2 independent search, photometry, cosmology pipelines  >500 SNeIa over 5 yrs with spectroscopic type SNLS in a nutshell

26. www.astro.uvic.ca/~pritchet SNLS – multiband  SNLS provides the definitive high-z SN dataset for the next 5+ years. Multi-band g’r’i’z’ photometry is the key:  Wide z range 0.2-0.9  Better control over systematics: SN colour evolution  Better control over dust: Extinction corrections using rest-frame U-B & B-V  Better control over k-corrections: wider wavelength coverage  Better estimates of rest-frame B-band luminosities

27. www.astro.uvic.ca/~pritchet 2 pipelines Data stays in Hawaii, remote real-time access 90% agreement i’~24 Short turnaround (6 hr to spec candidates) Two Search Pipelines (Ca, Fr) K. Perrett

28. www.astro.uvic.ca/~pritchet >1700 since Aug 2003! Detections 04D2ca z=0.83 Mar 10 ACS ~10 -4 of total Megacam area

29. www.astro.uvic.ca/~pritchet  D2  Cosmos  ACS imaging  ~7 x 7 arcsec +-  Note diversity

30. www.astro.uvic.ca/~pritchet Rolling Search  griz (redshift 0.2-0.9)  2-3 day sampling restframe  12 month observing

31. www.astro.uvic.ca/~pritchet Typical light-curves z=0.36 z=0.91

32. www.astro.uvic.ca/~pritchet Spectroscopy CFHTGemini-N

33. www.astro.uvic.ca/~pritchet Follow-up Spectroscopy (types and redshifts) Keck (~8 nights/yr) Ellis / Perlmutter VLT (120 hr/yr) France/UK: FORS1/2 to get types & redshifts for SNe (0.3 < z < 0.8) Gemini N & S (120 hr/yr) Canada/UK/US GMOS to get types/redshifts for SNe (0.6 < z < 0.9) More 8-10m time than CFHT time

34. www.astro.uvic.ca/~pritchet N(z) to 2006 (N ~ 300)

35. www.astro.uvic.ca/~pritchet SNLS: Current and projected numbers Currently >350 spec confirmed SNe Ia 400-500 spec confirmed SNeIa by survey end (>1000 total)

36. www.astro.uvic.ca/~pritchet  Historical Background  Supernova Cosmology  SNLS Overview  SNLS Results  Other SN Science  Conclusions/Future

37. www.astro.uvic.ca/~pritchet Distance estimator: stretch and colour  Distance estimator used:  s, c terms dominate; no need for other terms s – “stretch” corrects for light-curve shape via α “c” – B-V colour corrects for extinction (and intrinsic variation) via β

38. www.astro.uvic.ca/~pritchet First Year Cosmology (Astier et al. 2006) First year results (72 SNe Ia) consistent with an accelerating Universe: Ω M =0.263 in a flat universe Intrinsic disp.: 0.13 ± 0.02 Low-z: 0.15 ±0.02 SNLS: 0.12 ± 0.02 z’ errors – now observing 3x longer

39. www.astro.uvic.ca/~pritchet w = -1.02 ± 0.09 w = -1.02 ± 0.09  N=71, one year, SNLS+low z only  w to ~±0.05 by 2008 (why not +-0.03?) Astier et al 2006

40. www.astro.uvic.ca/~pritchet WMAP3 constraints  Spergel et al 2007 Assumptions: flat universe, perturbations in dark energy

41. www.astro.uvic.ca/~pritchet  2007 – prelim!  ~230 out of 270 SNeIa, to Aug 2006  Fit - w=-1 SNLS 3 rd year analysis Preliminary Cuts: Stretch 0.75<s<1.25 Colour Light curve coverage Intrinsic scatter: SNLS ±0.09 Low z ±0.13

42. www.astro.uvic.ca/~pritchet Residuals vs. SFR Passive galaxies Green=moderate star formation Blue=active star formation

43. www.astro.uvic.ca/~pritchet Addressing systematics  The control of systematics will define how accurately w and especially dw/dz will be determined  Large sample size of SNLS will allow subsample tests to investigate role of systematics Largest systematics currently are:

44. www.astro.uvic.ca/~pritchet Systematics …  ZP uncertainty ±0.04 in w  Improve mosaic uniformity to better than 1% (done)  Tie calibration to CALSPEC standards (precise flux standards)  Tie low and high z SNe together on uniform photometric system (SDSS-II)

45. www.astro.uvic.ca/~pritchet Systematics …  k-corrections (Hsiao et al 2007)  Based on 800 individual spectra (Suspect, etc)  Ellis et al 2007 UV

46. www.astro.uvic.ca/~pritchet Systematics …  Malmquist Bias ±0.025 in w (Perrett 2007)

47. www.astro.uvic.ca/~pritchet Systematics …  Redshift dependent population changes Sullivan et al …  Redshift evolution in SN properties Conley et al, Bronder et al …  Selection by SN photo-z? Sullivan et al 2005 1000 candidates – how to prioritize for followup? Defines success of survey. Photometric pre-selection. Fits early-time SN light- curves, returns probability of the candidate being a SN Ia.

48. www.astro.uvic.ca/~pritchet  Historical Background  Supernova Cosmology  SNLS Overview  SNLS Results  Other SN Science  Conclusions/Future

49. www.astro.uvic.ca/~pritchet Other SN science  Howell et al 2006 (Nature, Sep 2006) – SN 03D3bb – a super-Chandra mass SN Ia – evidence for double degenerate merger?  Sullivan et al 2006 – SNIa rate depends strongly on host SFR  Pritchet et al 2007 - Interpretation of SNIa rate vs. SFR diagram, nature of SNIa Progenitors  Neill et al 2006 – best determination of absolute SN Ia rate  Conley et al 2006 – SN light curve shapes are identical at low and high z  Nugent et al 2006 – first ever SN II Hubble diagram

50. www.astro.uvic.ca/~pritchet SN Ia Progenitors Single Degenerate - white dwarf + evolving secondary (M=1.4 Msun at explosion) Double Degenerate - 2 white dwarfs (M >= 1.4 Msun at explosion) Key point: white dwarf max mass = 1.4 Msun (Chandrasekhar mass)

51. www.astro.uvic.ca/~pritchet SNLS-03D3bb (Howell et al. 2006)  z=0.24, star-forming host  Most luminous SNIa ever discovered (M V =-20.0, 10 billion Lsun)  Lies off the stretch-L relation - too bright for its stretch s=1.13 by 4.4 sigma

52. www.astro.uvic.ca/~pritchet 03D3bb  Requires 1.3 Msun of 56 Ni to power light curve, 2Msun total mass  “normal” SNIa – 0.6 Msun of 56 Ni  03D3bb is 2.2x brighter, therefore has 2.2x Ni mass  Detailed calculation using Arnett models agrees well  Mass > Chandra mass of 1.4 Msun!

53. www.astro.uvic.ca/~pritchet 03D3bb  Low velocity of ejecta (8000 km/s)  Also implies super-Chandra mass  Conclusion: either (i) a rapidly rotating WD, or (ii) WD-WD merger  Implications for cosmology (this object was not used in Astier et al 2006)

54. www.astro.uvic.ca/~pritchet Other SN science  Howell et al 2006 (Nature, Sep 2006) – SN 03D3bb – a super-Chandra mass SN Ia – evidence for double degenerate merger?  Sullivan et al 2006 – SNIa rate depends strongly on host SFR  Pritchet et al 2007 - Interpretation of SNIa rate vs. SFR diagram, nature of SNIa Progenitors  Neill et al 2006 – best determination of absolute SN Ia rate  Conley et al 2006 – SN light curve shapes are identical at low and high z  Nugent et al 2006 – first ever SN II Hubble diagram

55. www.astro.uvic.ca/~pritchet SNeIa in Star-Forming Galaxies Mannucci et al 2006 Scannapieco and Bildsten 2006

56. www.astro.uvic.ca/~pritchet m = 1.10+-0.12, n = 0.84+-0.09 A=5.1E-14 SNe/yr/Msun B=4.1E-4 SNe/yr/(Msun/yr) B needed at 99.99% confidence cf. Scannapieco and Bildsten 2005 (m=1, n=1) Bivariate fits give m,n close to 1 Sullivan et al 2006

57. www.astro.uvic.ca/~pritchet SN Ia rate depends on SFR SFR ½

58. www.astro.uvic.ca/~pritchet Meaning of A٠M + B٠SFR  Does this imply two paths to SNeIa? …  … or is there a simple unifying picture that can be used to understand the A+B prescription for the SNIa rate?  Why do the A and B values have the values that are observed?  Continuum of delay times – more natural?  Why ~√SFR dependence rather than ~SFR?

59. www.astro.uvic.ca/~pritchet  Single degenerate scenario  Delay time depends on evolutionary timescale of secondary - T(evol) ≈ T(ms)  Simple SFR(t) ~ t -η to allow for range of ages Toy Model

60. www.astro.uvic.ca/~pritchet Models vs Observations  Locus of WD formation rates independent of SFR(t)  1% of WD’s become SNeIa  1% agrees with models (roughly)  1% agrees with MW (roughly)  Disagrees with clusters (10-20%)  Note that 1% eff is constant from active to passive galaxies! age

61. www.astro.uvic.ca/~pritchet Meaning  Single component model – not A+B  Continuous distribution of delay times  Rate in active and passive galaxies both explained  Only physics is evol timescales  Single free parameter normalization - f SNIa

62. www.astro.uvic.ca/~pritchet Efficiency vs mass  1 Msun main sequence stars find it very difficult to get to the Chandra mass and make a Type Ia SN Close binaries M1 < 2Msun make a He WD, not a C+O WD Mass arguments: 1 Msun on the m.s. makes a 0.5 Msun WD, hard to imagine 2 x 1 Msun making a 1.4 Msun WD Most of companions to 1 Msun stars haven’t evolved yet binary frequency lower for low mass objects (?) Therefore fraction of WD’s that make SNeIa should be much lower at low masses (>10x).

63. www.astro.uvic.ca/~pritchet Effects of efficiency  Normalized at high mass (short timescale) end  Assume efficiency drops by 10x from M=3 to 1 Msun (conservative) Single degenerate model cannot explain all SNeIa. Some other mechanism must be involved for at least some SNeIa.

64. www.astro.uvic.ca/~pritchet Cosmic SFR(z) Hopkins 2006

65. www.astro.uvic.ca/~pritchet SNR predictions from SFR(z)  Dot-dash=A+B  normalization arbitrary  Per Mpc^3

66. www.astro.uvic.ca/~pritchet Poznanski 2007 Dahlen 2004 Neill 2006

67. www.astro.uvic.ca/~pritchet  Historical Background  Supernova Cosmology  SNLS Overview  SNLS Results  Other SN Science  Conclusions/Future

68. www.astro.uvic.ca/~pritchet Conclusions  w = -1 (preliminary) from 3 rd year data (N=230).  Dark energy resembles pure cosmological constant (vacuum energy).  Most accurate estimate of w yet  SNIa rate depends on SFR  progenitors found in young and old stellar populations  Natural explanation from evolutionary timescales  1% of white dwarfs become SNeIa  SNeIa not only from single degenerate progenitors  ~400-500 SNeIa with spectroscopy by 2008, >1000 total  SNLS-2? ~60 deg^2, z<0.7, N=3000:  Stay tuned!

69. www.astro.uvic.ca/~pritchet More SNLS information  http://legacy.astro.utoronto.ca/  http://legacy.astro.utoronto.ca/ - database (Perrett) http://legacy.astro.utoronto.ca/  www.cfht.hawaii.SNLS  www.cfht.hawaii.SNLS – people, papers, … www.cfht.hawaii.SNLS

70. www.astro.uvic.ca/~pritchet Special Mention … Andy Howell – PDF U.Toronto Melissa Graham U Victoria Alex Conley – PDF U Toronto Eric Hsiao U Victoria Mark Sullivan – PDF U Toronto Kathy Perrett – PDF U Toronto, Ms. Data Dave Balam, RA, U Victoria