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Review of SNLS results

Review of SNLS results. The S uper n ova L egacy S urvey Cosmology results SNe Ia : usable for precision cosmology ? Conclusions. 04D1dc. SNLS at CFHT. The survey (2003-08): - four 1 °x1° fields - each field observed every 3-4 nights during 6 months MegaCam :

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Review of SNLS results

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  1. Review of SNLS results The Supernova Legacy Survey Cosmology results SNe Ia : usable for precision cosmology ? Conclusions 21 May 2008

  2. 04D1dc SNLS at CFHT • The survey (2003-08): - four 1°x1° fields - each field observed every 3-4 nights during 6 months • MegaCam : - 1°x1° CCDimager - 340 millions of pixels - pixel resolution: 0.18“ - fourfilters (400-1000nm) • Spectroscopy: time allocated on 8-10 meter class telescopes ~500confirmedSNe Ia in5 yearswith redshifts in0.1 – 1.2 21 May 2008

  3. SNLS "rolling search" large and homogeneous sample of high-z spectroscopically confirmed SNe Ia, measured with good photometric accuracy 21 May 2008

  4. multi-band LC’s : test compatibility with SNIa model (trained on SNIa lightcurves and spectra) a SNIa lightcurve spectroscopy triggered  type Ia confirmed, z=0.627 i’, r’, z’, g’ filters apparent B flux : mB*, (B-V) colour c and stretch s see e.g J.Guy et al., A&A 466 (2007) 11 21 May 2008

  5. Cosmology with SNe Ia • SNe Ia are (assumed to be) standard candles : known luminosity mB*fromB* L(c,s)/4πdL2with dL(z,H0,ΩM,ΩΛ,w,..) • Distance estimator : B = mB* - MB + (s-1) - c apparent rest-frame maximum light magnitude reference absolute B-band magnitude (B-V)colour variability (intrinsic variation and extinction) lightcurve shape variability + intrinsic dispersionterm, int allowed in cosmological fits to account for our lack of knowledge about SNe 21 May 2008

  6. 1st year results P.Astier et al., A&A 447 (2006) 31 fainter residuals to (0.26,0.74): int: 0.13± 0.02 Low-z: 0.15±0.02 High-z: 0.12±0.02 older  First year result (71 SNe)consistent with an accelerating Universe 21 May 2008

  7. M+=1 Cosmological parameters w=-1 if ΩM+ΩΛ=1: ΩM=0.263±0.043±0.032 (SNLS,w=-1) w=-1.023±0.090±0.054 (SNLS+BAO) 21 May 2008

  8. Preliminary 3rd year result SNLS3 result (~250 SNe)agrees with SNLS1 result, w consistent with -1 within 6% (SNLS+BAO+WMAP5) 21 May 2008

  9. SNe Ia : usable for precision cosmology ? Distance estimator : B = mB* - (MB - (s-1) + c) MB, ,  assumed to be z-independent Is that so ?  compare properties of SN sub-samples split by redshift, host activity… 21 May 2008

  10. mB* - MB + (s-1) - c – 5 log10(dLfit c-1 H0) blue: z<0.15 / black: z>0.15 residuals without c-term residuals without s-term brighter slower bluer ‘’brighter-slower relationship’’ ‘’brighter-bluer relationship’’  consistent behaviour for nearby and distant SNe Ia (1st year data) P.Astier et al., A&A 447 (2006) 31 21 May 2008

  11. stretch-corrected lightcurves 73 SNe z<0.9 – 2 years of data • SN Ia rise-times consistent at 1σ • low-z vs high-z SNe Ia • passive/active host galaxies A.Conley et al., AJ 132 (2006) 1707 21 May 2008

  12. Active hosts Passive hosts SN Ia environment SN Ia rate per unit mass per year SN stretch depends on host activity  SN Ia rate is a function of the host stellar mass andSFR 10 10 10 10 10 Star formation rate per unit mass M.Sullivan et al., ApJ 648 (2006) 868 Brighter, slower SNe occur mostly in star-forming galaxies (2 years of data) 21 May 2008

  13. Two-component rate modelisation1 SNRIa(t) = AMtot + B dM/dt(t) galactic stellar massSFR old stars prompt SNe evolved galaxies star-forming galaxies • Fit A and B from SNLS data • Use fitted A, B values and a model2 for SFR(z) to predict rates vs redshift • Compare predicted rate with measurements 1Scannapieco, Bildsten (2005) 2 Cosmic SFH from Hopkins & Beacom (2006) 21 May 2008

  14. Implication: Predicted mix of two SN populations evolves with z Average SN stretch will evolve with z 21 May 2008

  15. D.Howell et al., ApJ 667 (2007) 37 SNLS stretch evolution with z: predictions agree with data <stretch> + 8% for z=0.03-1.12 <intrinsic brigthness> +12% If is the same for old/prompt SNe, this will not affect cosmology Need more data to test , values from sub-samples split by stretch or host type Stay tuned ! 21 May 2008

  16. Conclusions • SNLS: efficient high-z SN Ia detection, optimised temporal sampling, very good photometric accuracy. • Cosmology:~250 SNe in SNLS3. Constraints on m, w consistent with SNLS1 results, accuracy on w from 9 to 6% (stat). • Are SNe Ia good cosmological probes ? • Average SN Ia properties evolve with redshift. So far, no bias in cosmology detected. • Larger samples needed to test if the empirical luminosity-shape or color relations need to be refined. 21 May 2008

  17. BACK-UP SLIDES 21 May 2008

  18. A possible type Ia explosion mechanism  reproducible intrinsic luminosity : SNe Ia ~standard candles 21 May 2008

  19. Spectroscopic time allocated on 8-10 meter class telescopes more 8-10m time than CFHT time ! 21 May 2008

  20. SNLS SNIa data sample September 06: >350 spec confirmed Ia >500 spec confirmed Ia by end of June 08 More than 1000 Ia in total 21 May 2008

  21. SNLS data analysis An example of raw image: entire 4x9 CCD mosaic one exposure of 300sec filter r (<>=620nm) size: 1.4 Gb 2004/10/21 whole survey: 15 Tb 21 May 2008

  22. Reference image Current image Subtraction SN SN detections SN Ia events found by CCDimage subtraction: Many steps: image cleaning and alignment, photometric calibration, match reference and current image qualities… 21 May 2008

  23. M+=1 DE equation of state w=1/3 radiation w=0 matter w>-1 quintessence w=-1 cosmological constant if ΩM+ΩΛ=1: ΩM=0.271±0.021±0.007 w=-1.023±0.090±0.054 (SNLS+BAO) 21 May 2008

  24. Systematics, 1st year paper photometric accuracy selectionbias SN Ia model SN Ib/Ic contamination:  0.5 in the 1st year sample 21 May 2008

  25. Comparison with previous SN results Knop et al, 2003 (HST+SCP) : 52 SNe,dotted contours SNLS 1st year: 71 SNe, solid countours SNLS projected end of survey shaded area the superior color and time sampling leads to tighter constraints 21 May 2008

  26. Preliminary SNLS3 Intrinsic colour vs dust extinction Colour—luminosity relationship inconsistentwith MW-type dust Best-fit: β~3 MW-dust: β≡RB=4.1 β=4.1 Residual without c-correction SN Colour (c) M.Sullivan, STScI, may 2008 21 May 2008

  27. Preliminary SNLS3 180 high-z SNe Residual without c-correction Colour correction required in all host types Either: Passive hosts have dust? An intrinsic relation dominates over dust? Star-forming hosts 40 high-z SNe Large “local” SN surveys covering a wide wavelength range (inc. near-IR) urgently needed to disentangle this Residual without c-correction Passive hosts M.Sullivan, STScI, may 2008 SN Colour (c) 21 May 2008

  28. Preliminary SNLS3 stretch Determine  (luminosity correction),  (color correction), from subsamples split by… high s s>1 galaxy type s<1 Tension? low s spiral Early days… larger samples will be definitive elliptical M.Sullivan, STScI, may 2008 21 May 2008

  29. Spectroscopic corollaries T.J.Bronder et al., A&A 477 (2008) 717 SiII equivalent width distributions (residuals / low-z beahviour) □ E/S0 ■ Spirals Lower EWs in late-type galaxies, whatever the redshift SNe Ia in late-type (star-forming) galaxies are brighter (more 56Ni) and thus hotter  more ionisation  less intermediate mass elements (Ca, Si). (87 SN Ia spectra from Gemini – 3 years of data) Lower EWs in late-type galaxies, whatever the redshift 21 May 2008

  30. SNe Ia as standard candles ~flux • 1990s: a simple temporal stretch correction aligns the light-curves in a sample of nearby SNe Ia • Study cosmology with distant SNe Ia • The High-Z project (95-97): 10 SNe Ia in 0.3<z<0.97 • The SuperNova Cosmology Project (93-98): 42 SNe Ia in 0.18<z<0.83 days days 21 May 2008

  31. SNLS vs 1st generation experiments Ex: the High-Z experiment: • Small CCD camera  few nights of observation  only 10 high z SNe Ia • poor light-curve sampling • Only two filters 21 May 2008

  32. 0.01 0.1 1 z Cosmology from SNe Ia : 1997-98 fainter  further back in time more redshift  more expansion ~ apparent fluxB = L/4πdL2 with dL(z,H0,ΩM,ΩΛ,w)  the Universe expansion isaccelerating 21 May 2008

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