1. Exploring the global properties of SNe Ia
Paolo A. Mazzali
Max-Planck Institut fϋr Astrophysik, Garching
Astronomy Department and
RESearch Centre for the Early Universe,
University of Tokyo
Istituto Naz. di Astrofisica, OATs

2. Spectra of Supernovae: the photospheric phase
SN Ia
SN II
SN Ic
SN Ib
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Galileo Galilei Institute

3. SNe Ia have similar light curves Are they also equally luminous?
Branch & Tammann 1992
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Galileo Galilei Institute

4. 87 SNe Ia: Observed B Light Curves
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5. 87 SNe Ia: Normalised B Light Curves
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Galileo Galilei Institute

6. 87 SNe Ia: Stretched B Light Curves
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Galileo Galilei Institute

7. The Phillips Relation (Absolute Magnitude - Decline Rate)
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8. Galileo Galilei Institute
Cosmology with SNe Ia
Distant SNe are FAINT for their redshift
From B.Schmidt
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9. Galileo Galilei Institute
Cosmology with SNe Ia
Riess et al. 1999
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Galileo Galilei Institute

10. SN Ia as distance indicators
fainter
brighter
nearer
further
High-z SN Search Team
(Riess et al. 1998)
Supernova Cosmology Project
(Perlmutter et al. 1999)
empty universe
surprising result:
Distant SNe Ia appear fainter
than standard candles in an
empty Friedmann model
of the universe!
SN Ia luminosity distances
indicate
accelerated expansion!
Are SNIa Standard Candles
independent of age?
Or is there some evolution
of SN Ia luminosity with age?
Spectroscopy is a
powerful tool to
search for differences!
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Galileo Galilei Institute

11. Cosmology with SNe Ia: the Cosmological Constant
From E.Baron
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Galileo Galilei Institute

12. Bolometric Light Curves
Contardo et al. 2000
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13. Supernova Spectra evolve
Soon after explosion (first few weeks), ejecta density is high enough for a `pseudo-photosphere’ to form.
“Photospheric Epoch”
(early time)
P-Cygni Profiles superposed on continuum
Later on, photosphere disappears as densities decrease.
“Nebular Epoch”
(late time)
Emission-line spectrum
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Galileo Galilei Institute

14. SNIa Spectral Evolution
Gomez & Lopez 1998
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Galileo Galilei Institute

15. Galileo Galilei Institute
Early-time spectrum
Homologous expansion
(v ≈ R)
Ejecta are dense
“Photospheric Epoch”
absorption
continuum
τ=1
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16. Galileo Galilei Institute
Early-time spectrum
Lines have P-Cygni profiles with
But velocities are high:
many lines overlap:
“Line Blanketing”
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17. Galileo Galilei Institute
SNe maximum
“Branch normals”
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18. SNe Ia @ 20 days after maximum
“Branch normal”
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19. Galileo Galilei Institute
Late-time spectra
Ejecta are thin:
“Nebular Epoch”
Gas heated by deposition of γ’s and
cooled by forbidden line emission
Spectrum: no continuum.
Emission line profiles depend on velocity, abundance distribution.
Homologous expansion, homogenous density and abundance: parabolic profiles
τ < 1
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Galileo Galilei Institute

20. SNe Ia: late-time spectra
Δm15(B)
1.93
1.77
1.27
1.51
0.87
Mazzali et al. 1998
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Galileo Galilei Institute

21. Thermonuclear SNe (Type Ia) White Dwarf in Binary System
WD accretes H until
MWD~1.4M⊙, T~109K
Thermonuclear burning (C burning) to NSE
Explosion (KE~1051 erg)
Total disruption of WD
56Ni produced (~0.7M⊙) RG
CO-WD
C, O
Si, S
56Ni
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22. Type Ia SN 1996X spectral evolution
Salvo et al. 2000
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23. The Classical SN Ia explosion model: W7
Branch et al. 1985
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Galileo Galilei Institute

24. I. Using observables to understand SNe Ia
Questions
Properties of SNe Ia (eg Phillips rel’n)
Mode of explosion (deflagration, delayed detonation, other even less reasonable modes…)
Cosmology?
Methods
Look at/model spectra & light curves
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25. Galileo Galilei Institute
What we need
Excellent photometric and spectroscopic coverage of a number of nearby SNe Ia
Comparison with the high-z sample
3D models of the explosion
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Galileo Galilei Institute

26. How we get it: the EU-RTN
16 well observed SNe ( )
 Abundance Tomography
 More signatures of CSM interaction
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27. Galileo Galilei Institute
Data: SNe 2002bo, 2003du
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Galileo Galilei Institute

28. Modelling early-time spectra
Monte Carlo code
Composition
Density
Luminosity
Velocity
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29. Abundance Stratification
Model sequence of spectra to derive composition layering
How did the star burn?
Stehle et al 2005
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Galileo Galilei Institute

30. Model late-time spectra
Monte Carlo LC code + NLTE nebular code
No radiative transfer
Get full view of inner ejecta (56Ni zone)
Estimate masses
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31. Composion in a typical SN Ia
Elements more mixed than in typical 1D models
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32. Galileo Galilei Institute
Test: Light Curve
Monte Carlo code
Use W7 density
Composition from tomography
(56Ni ~0.50M⊙ )
 Model LC matches data very well
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33. II. Outer regions of the ejecta: HVFs
Nearly all SNe show very high velocity (~20000 km/s) absorption features (HVF) in Ca II (some also in Si II)
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34. HVFs come in various forms
Mazzali et al. (2005) Tanaka et al. (2006)
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35. Galileo Galilei Institute
What makes the HVFs
Abundance enhancement unlikely
Density enhancement more reasonable
Ejection of blobs or CSM interaction?
Blobs: line profiles depend on orientation
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Galileo Galilei Institute

36. Galileo Galilei Institute
Distribution of HVFs
Any model should reproduce the observed distribution of HVF wavelength (blob velocity) and strength (optical depth, covering factor)
Single blob does not
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37. Need a few blobs or a thick torus
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38. Use blobs to fit spectra
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39. Galileo Galilei Institute
3D Simulations (MPA)
Reinecke et al. 2000
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40. Galileo Galilei Institute
III. The Global View
Late time spectra suggest M(56Ni)  Δm15(B) [ M(Bol)]  v(Fe)
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41. Galileo Galilei Institute
Role of 54Fe, 58Ni
Stable Fe group isotopes radiate but do not heat
Some anticorrelation between 56Ni and (54Fe, 58Ni)
Very good correlation beween Σ(NSE) and Δm15(B)
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42. Galileo Galilei Institute
Composition Layering
Outer extent of Fe zone varies ( Δm15(B), Lum)
Inner extent of IME matches outer extent of Fe
Outer extent of IME ~ const.
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43. Include 54Fe, 58Ni: “Zorro” diagram
A basic property of SNe Ia
Mass probably constant
Amount of burned material also probably constant
KE ~ const
What does it all mean?
Delayed detonation?
Multi-spot ignited deflagration?
Other possibilities….?
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44. IV. Role of Fe-group, IME on LC
56Ni: light, opacity, KE
54Fe, 58Ni: opacity, KE
IME: KE, (some opacity)
CO (if any): little opacity
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45. Explaining Phillips’ Relation
56Ni: light, opacity, KE Reproduce
54Fe, 58Ni: opacity, KE Phillips’ Relation
IME: KE, (some opacity)
CO (if any): little opacity (Mazzali et al. 2001)
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Galileo Galilei Institute

46. Galileo Galilei Institute
-7 days
Mazzali et al. 2001
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47. Galileo Galilei Institute
Maximum
Mazzali et al. 2001
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48. Galileo Galilei Institute
+15 days
Mazzali et al. 2001
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49. Using Zorro to reconstruct Phillips’ Rel’n
Use composition to compute LC parameters 
Derive Phillips Relation 
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50. Galileo Galilei Institute
Effect of 54Fe, 58Ni
Amount of 54Fe, 58Ni may be a fn. of WD metallicity (Timmes et al. 2003)
Ratio 56Ni/NSE affects light, not KE or opacity
LCs w/ different peak brightness, same decline rate
May explain spread in Phillips’ Relation.
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51. Galileo Galilei Institute
Effect on Cosmology?
Evolution in Z may mimic cosmology
Star-forming galaxies at z~1 may have been metal-rich w/r to present (Galaxy Downsizing)
More neutronization  dimmer SNe with same LC
May be consistent with Ωm=0.3, ΩΛ=0.0 Universe, but not with Ωm=1 Universe
(Podsiadlowski et al. 2006)
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52. Uncertainty on cosmological parameters
A variation in Z may be interpreted as a variation in Ωm, w0, or wa.
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53. Galileo Galilei Institute
Conclusions
There is some regularity among SNe Ia (surprise surprise…)
Ejecta reflect stratified composition of models
Total mass burned may be constant
56Ni determines luminosity (not new)
Total NSE determines LC shape
Degree of neutronization can give rise to dispersion in luminosity-decline rate relation
Z evolution may confuse cosmological parameters
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54. Effect on scale factor with Z
Different cosmologies (Linder et al) v. Metallicity evolution
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