snls-03d3bb andy howell university of toronto and the supernova legacy survey (snls)
TRANSCRIPT
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SNLS-03D3bb
Andy Howell
University of Toronto
and the Supernova Legacy Survey (SNLS)
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Hostz =
0.2440
81.050.093.8log
galM
HST
CFHT
CFHT
From PEGASE 2 fits to host ugriz photometry:
02.01
81.050.0
26.1
93.8log
SFR
M gal
M yr-1
Formally implies host age of 0.7 Gyr, though highly uncertain
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Si II velocityLow-z data from Benetti et al. 2005
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LightcurveV=20.5 ± 0.06
MV = -19.94 ± 0.06
Use only r, i fit
s = 1.13
Sparse LC from early days of survey
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V magnitude distribution
MV = -19.94 ± 0.06
Low-z Astier et al. sample
2.2 times the luminosity of median SN Ia
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56Ni mass
)(tS
L=M
r
bolNi α
/111e101.43+
/8.8e106.31=S rt43rt43 erg s-1 M
-1
Arnett’s rule: Luminosity at maximum is proportional to spontaneous energy deposition by radioactive decay.
: ratio of bolometric to radioactivity luminosities
S : energy per second per solar mass from radioactive deacay
Using tr = -19.5 (Conley et al. 2006), = 1.2 (Nugent et al. 1996), get MNi = 1.29 ± 0.07 M
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Velocity from kinetic energy
WD
bnke M
)E(E=v
2
)f+(fME=E IMEFeWDFen 0.76
Energy from burning to Fe peak:
51101.55=EFe erg s-1 M-1
3 kinds of elements: Fe-peak, IME, unburned C/O
KE is nuclear energy minus binding energy
Burning to Si produces 76% as much
56Ni is 70% of Fe-peak elements:
FeWDNi fMM 7.0
Binding energy (Yoon & Langer 2005)- 1.4 M WD: 0.5e51 erg- 2.0 M WD: 1.3e51 erg
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Implications - Progenitors
• Double degenerate model: merger of two massive WDs can produce super-Chandra product. In youngest populations, only massive WDs exist. Before 0.9 Gyr, combined WD mass must be > Chandrasekhar mass.
• Single degenerate model: rapid rotation could support 2 solar mass WD according to Yoon & Langer 2005. Young pop. favored for higher starting WD, secondary masses.
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Implications
• The most luminous SNe occur in young populations
• Super-Chandra model predicts more luminous SNe in younger populations
• Chandra model has no explanation for this.
• Could WD mass partially drive luminosity fluctuations in SNe Ia?
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Conclusions - Observations
• MV=19.94 ± 0.06, brightest SN Ia ever observed (with the possible exception of the interacting SN 2002ic)
• SiII velocity at +2d among the lowest seen, 8000 km/s
• SiII strong relative to CaII at +2d, in contrast with other SNe Ia
• CII near maximum implies the presence of unburned material deep into the SN
• Low-mass, blue host implies a young progenitor age
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Conclusions - Interpretation
• Arnett’s law implies ~1.3 M 56Ni.
• If ~40% of elements are non-56Ni, MWD ~ 2.1 M
• High 56Ni mass implies large nuclear energy, which should produce large velocities in Chandrasekhar model.
• Low velocity consistent with increased binding energy of super-Chandra model.
• Young galaxy consistent with expectations from Super-Chandra model
• SNLS-03D3bb meets every expectation of the super-Chandra model
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Conclusions - Cosmology
• WD mass may partially drive SN Ia luminosity
• SNLS-03D3bb does not follow stretch-luminosity relationship (it is too bright by 4.4 sigma).
• “Evolution” in SNe with redshift?• SNLS-03D3bb was thrown out of Astier
et al. (2006), but less extreme examples could be in data set.