1. A Step towards Precise Cosmology from Type Ia Supernovae Wang Xiaofeng Tsinghua University IHEP, Beijing, 23/04, 2006

2. Outlines What is Supernova? The light curve properties of SNe Ia The empirical calibration methods for SNe Ia New cosmological distances from SNe Ia and the implications for cosmology

3. Supernova Explosion! SN 2005mf

4. Supernova Search 300-400/year since 1998 A New record: 365 in 2005!

6. Stellar evolution and supernova explosion

10. Raw Hubble diagram of SNe Ia

11. Luminosity Function of SNe Ia (wang et al. 2005b)

12. The environmental effect on SN luminosity

13. SN Ia correlations  m15 relation  BATM Phillips (1993), Hamuy et al. (1996), Phillips et al. (1999) MLCS  MLCS2k2 Riess et al. (1996, 1998), Jha et al. (2003) Stretch  SALT Perlmutter et al. (1997), Goldhaber et al. (2001), Guy et al. (2005)  C12 method Wang et al. (2005a, b)

14. The template method (Phillips 1993, Hamuy et al. 1996)

15. The light curve fitting by template

16. Luminosity vs. decline rate Piskovski-Phllips relation Phillips et al. 1999

17. The SN Ia luminosity can be normalised Bright = slow Dim = fast BVIBVI Riess et al. 1996 MLCS method

19. The reasons underlying the light curve correlation Deductions Slower SNe Ia are more luminous --more energy radiated More luminous SNe Ia have slower declines at late phases (Phillips et al. 1999, Contardo et al. 2001) -- slower release of the energy Slower SNe Ia have larger expansion velocities (Mazzali et al. 1998) --less efficient trapping of  -rays Contardo et al. 2000; data for SN 1991 from Strolger et al. 2002

20. The nearby SNe Ia distance accuracy around 8-12% Evidence for good distances, but not good enough for precise cosmology Tonry et al. 2003

21. The post-maximum color calibration (Wang et al. 2005)

22. SN Peak Luminosity vs.  C 12 distance accuracy around 4-5%

23. Treatment of the host galaxy reddening

25. Non-standard dust in other galaxies (Wang et al. 2006a) Smaller than the standard values of 5.5 in U, 4.3 in B, 3.3 in V, and 1.8 in I in the Milkyway SN explosion may change the size of the dust grains or the distribution of the dust in CSM

26. Second parameter correlations

27. The residual correlations

28. The Most Precise Hubble diagram from SNe Ia

29. Normalising Type Ia Supernovae –light curve and color curve shape corrections what is the determining parameter? –Ni mass  trapped energy  light curve shape (affected also by opacity?) –temperature  colour –explosion mechanism? What are the subluminous objects? a faint end of normal or distinct type ?

30. Applications to SNLS data

31. Comparison between different methods: magnitudes at maximum (TF Vs. SF)

32.  C 12 vs. Stretch factor

33. distribution of Color parameters and Extinction Nearby vs. distant  C 12 : 0.44 vs. 0.33 E(B-V ） host : 0.062vs.0.077

34. Calibration difference

35. Correcting relations conditions b B R B b V R V All(excl. 91bg-like) 1.69(10), 3.45(11) 1.47(10), 2.43(12) If E(B – V) < 0.40 mag 1.64(09), 2.84(18) 1.43(10), 1.81(20) If E(B – V) < 0.30 mag 1.60(10), 2.93(22) 1.42(10), 1.86(22) If E(B – V) < 0.20 mag 1.65(10), 2.90(27) 1.45(10), 2.06(28)

36. Hubble diagram from  C 12 calibration

37. Cosmological results (for 131 well-sampled SNe Ia) N Fit parameters(  C 12 ) parameters(salt) 84 (  m,    (  m,    flat   (  m,     (  m,    flat  

38.  m -   contour

39.  m - w contour

40. New result