400 likes | 595 Views
A Step towards Precise Cosmology from Type Ia Supernovae Wang Xiaofeng Tsinghua University IHEP, Beijing, 23/04, 2006. Outlines. What is Supernova? The light curve properties of SNe Ia The empirical calibration methods for SNe Ia
E N D
A Step towardsPrecise Cosmology from Type Ia SupernovaeWang XiaofengTsinghua UniversityIHEP, Beijing, 23/04, 2006
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
Supernova Explosion! SN 2005mf
Supernova Search A New record: 365 in 2005! 300-400/year since 1998
Luminosity Function of SNe Ia (wang et al. 2005b)
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)
Phillips et al. 1999 Luminosity vs. decline ratePiskovski-Phllips relation
B V I MLCS method The SN Ia luminosity can be normalised Bright = slow Dim = fast Riess et al. 1996
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
The nearby SNe Ia distance accuracy around 8-12% Evidence for good distances, but not good enough for precise cosmology Tonry et al. 2003
SN Peak Luminosity vs. C12 distance accuracy around 4-5%
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
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 ?
Comparison between different methods: magnitudes at maximum (TF Vs. SF)
distribution of Color parameters and Extinction Nearby vs. distant DC12: 0.44 vs. 0.33 E(B-V)host: 0.062vs.0.077
Correcting relations conditions bB RB bV RV 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)
Cosmological results (for 131 well-sampled SNe Ia) N Fit parameters(DC12) parameters(salt) 84 (Wm,WL) 0.330.20,0.780.24 0.210.33, 0.65 0.44 (Wm,WL) flat 0.2790.026 0.268 0.043 65 (Wm,WL) 0.370.19,0.870.24 • (Wm,WL) flat 0.2730.029