a step towards precise cosmology from type ia supernovae wang xiaofeng tsinghua university ihep,...
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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
• New cosmological distances from SNe Ia and the implications for cosmology
Supernova Explosion!
SN 2005mf
Supernova Search 300-400/year since 1998
A New record: 365 in 2005!
SN classificationsTaxonomy Chart Spectroscopic classifications
Stellar evolution and supernova explosion
Type Iasupernovaewhite dwarf in binary stellar system
high H accretion rates
growing C/ O white dwarf
~Chandrasekhar mass (1.4 Msolar) contraction
high central density C fusion
thermonuclear explosion
Type I a: WD defl agration
Expanding, cooling optically-thick shell: 56Ni 56Co
cooling optically-thin: 56Co 56Fe
57Co, 44Ti, 22Na decay
Supernova Light curves
Riess et al. 1999
Raw Hubble diagram of SNe Ia
Luminosity Function of SNe Ia
(wang et al. 2005b)
The environmental effect on SN luminosity
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)
The template method (Phillips 1993, Hamuy et al. 1996)
The light curve fitting by template
Luminosity vs. decline rate Piskovski-Phllips relation
Phillips et al. 1999
The SN Ia luminosity can be normalised
Bright = slow Dim = fast
B
V
I
Riess et al. 1996
MLCS method
Stretch factor method
Goldhaber et al. 2001
stretch
The reasons underlying the light curve correlation
SN MB log(L) M(Ni)
SN1989B -19.37 43.06 0.57SN1991T -19.76 43.23 0.84SN1991bg -16.78 42.32 0.11SN1992A -18.80 42.88 0.39SN1992bc -19.72 43.22 0.84SN1992bo -18.89 42.91 0.41SN1994D -18.91 42.91 0.41SN1994ae -19.24 43.04 0.55SN1995D -19.66 43.19 0.77
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
The post-maximum color calibration(Wang et al. 2005)
SN Peak Luminosity vs. C12
distance accuracy around 4-5%
Treatment of the host galaxy reddening
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
Second parameter correlations
The residual correlations
The Most Precise Hubble diagram from SNe Ia
•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 ?
Applications to SNLS data
Comparison between different methods: magnitudes at maximum
(TF Vs. SF)
C12 vs. Stretch factor
distribution of Color parameters and Extinction
Nearby vs. distant
C12: 0.44 vs. 0.33
E(B-V)host: 0.062vs.0.077
Calibration difference
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)
Hubble diagram from C12 calibration
Cosmological results (for 131 well-sampled SNe Ia)
N Fit parameters(C12) parameters(salt) 84 (m, (m,flat
(m, (m,flat
m- contour
m- w contour
New result
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