type ia supernovae bruno leibundgut european southern observatory
TRANSCRIPT
Type Ia Supernovae
Bruno Leibundgut
European Southern Observatory
Supernova!
© Anglo-Australian Telescope© Anglo-Australian Telescope
© SDSSII
Supernovae!
Supernovae!
Riess et al. 2007
Supernova classificationbased on maximum light spectroscopy
Thermonuclear supernovae
Core-collapse supernovae
IISN 1979CSN 1980KSN 1987ASN 1999emSN 2004dt
IIbSN 1993J
IaTycho’s SN SN 1991TSN 1991bgSN 1992ASN 1998buSN 2001elSN 2002boSN 2002cxSN 2005hk
Ib/c
GRBsSN 1998bwSN 2003dhSN 2006aj
heliumno yes
Ic IbSN 1994ISN 1996NSN 2004aw
SN 1983N
silicon
yes no
hydrogen
no yes
Smith et al. 2007
Supernova types
thermonuclear SNe• from low-mass stars
(<8M)• highly evolved stars
(white dwarfs)• explosive C and O
burning• binary systems
required• complete disruption
core-collapse SNe• high mass stars
(>8M)• large envelopes
(still burning)• burning due to
compression• single stars (binaries
for SNe Ib/c)• neutron star
Energy sourcesgravity → core-collapse supernovae
• collapse of a solar mass or more to a neutron star
release of 1053 erg− mostly νe
− 1051 erg in kinetic energy (expansion of the ejecta)− 1049 erg in radiation
nuclear (binding) energy → thermonuclear supernovae
• explosive C and O burning of about one solar mass• release of 1049 erg
Type Ia Supernova
SN 1937C: Baade and Minkowski
Supernovae as standard candles
Uniform appearance• light curves
– individual filters
– bolometric
• colour curves – reddening?
• spectral evolution• peak luminosity
– correlations
Phillips et al. 1999
Jha 2005
SN Ia CorrelationsLuminosity vs. decline rate
• Phillips 1993, Hamuy et al. 1996, Riess et al. 1996, 1998, Perlmutter et al. 1997, Goldhaber et al. 2001
Luminosity vs. rise time• Riess et al. 1999
Luminosity vs. color at maximum• Riess et al. 1996, Tripp 1998, Phillips et al. 1999
Luminosity vs. line strengths and line widths• Nugent et al. 1995, Riess et al. 1998, Mazzali et al. 1998
Luminosity vs. host galaxy morphology• Filippenko 1989, Hamuy et al. 1995, 1996, Schmidt et al. 1998, Branch et al.
1996
Absolute Magnitudes of SNe Ia
SN Galaxy m-M MB MV MIDm15
1937C IC 4182 28.36 (12) -19.56 (15) -19.54 (17) - 0.87 (10)1960F NGC 4496A31.03 (10) -19.56 (18) -19.62 (22) - 1.06 (12)1972E NGC 5253 28.00 (07) -19.64 (16) -19.61 (17) -19.27 (20)0.87 (10)1974G NGC 4414 31.46 (17) -19.67 (34) -19.69 (27) - 1.11 (06)1981B NGC 4536 31.10 (12) -19.50 (18) -19.50 (16) - 1.10 (07)1989B NGC 3627 30.22 (12) -19.47 (18) -19.42 (16) -19.21 (14)1.31 (07)1990N NGC 4639 32.03 (22) -19.39 (26) -19.41 (24) -19.14 (23)1.05 (05)1998bu NGC 3368 30.37 (16) -19.76 (31) -19.69 (26) -19.43 (21)1.08 (05)1998aq NGC 3982 31.72 (14) -19.56 (21) -19.48 (20) - 1.12 (03)Straight mean -19.57 (04) -19.55 (04) -19.26 (0 6)Weighted mean -19.56 (07) -19.53 (06) -19.25 (0 9)
Saha et al. 1999
The strongest evidence ...
Type Ia Supernovae
Explosion physics relatively well understood• significant progress in the past decade
Radiation transport remains a big problem• simplifications can provide new insight into
the explosion models• progress in the ab initio calculations as well
– recent new ideas
Thermonuclear Supernovae
White dwarf in a binary system
Growing to the Chandrasekhar mass (MChand=1.4 M) by mass transfer from a nearby star
The “standard model”
© ESA
The “standard model”
He (+H)from binarycompanion
Explosion energy:
Fusion of
C+C, C+O, O+O
"Fe“
Density ~ 109 - 1010 g/cm
Temperature: a few 109 K
Radii: a few 1000 km
C+O,C+O,
M ≈ MM ≈ Mchch
There is a lot more to this – you need to contact your explosive theory friends
Supernova explosions
Courtesy F. Röpke
t=0.0s
Pushing simulations to the limit
t=0.6st=3.0st=10.0s
Courtesy F. Röpke
There is more after 10 seconds …
Radiation hydrodynamics• how do the photons escape the supernova• the observational fun starts here • (and the explosion calculations stop)
© Pete Challis, CfA
SN light curve calculations
Kasen 2006
SN 2001el
Spectral evolution
Kasen & Woosley 2007Stanishev et al. 2007
Courtesy S. Blondin
Are SNe Ia standard candles?No!
• large variations in– light curve shapes– colours– spectral evolution– polarimetry
• some clear outliers– what is a type Ia supernova?
• differences in physical parameters– Ni mass– ejecta mass
The diversity of SNe Ia
Recent examples have destroyed the standard candle picture• SN 2000cx, SN 2002cx
Candia et al. (2003)
Li et al. (2003)
Diverse SNe Ia
Phillips et al. 2007
SN 03D33dbHowell et al. 2006
Diverse spectral evolution
Branch et al. 2006
Benetti et al. 2005 Benetti et al. 2005
also at higher redshifts …
Blondin et al. 2006also Garavini et al. 2007Bronder et al. 2008
Polarimetry
Wang et al. 2006Wang et al. 2007
Polarimetry results
Very small continuum polarisation→overall shape appears fairly round
Partially strong line polarisation→distribution of individual elements could be
clumped
→inhomogeneous explosion mechanism?
→dependence on viewing angle?
Possible correlation with light curve shape parameter (Wang et al. 2007)
What is a SN Ia?
Peculiar cases abound …• SN 1991T, SN 1991bg• SN 1999aa, SN 1999ac• SN 2000cx, SN 2002cx• SN 2002ic• SN 03D3bb• SN 2005hk• and more
Hamuy et al. 2003
Howell et al. 2006Howell et al. 2006
Jha et al. 2006
Phillips et al. 2007
Global explosion parameters
Determine the nickel mass in the explosion from the peak luminosity• large variations (up to a factor of 10)
Possibly determine • total mass of the explosion or• differences distribution of the nickel, i.e. the
ashes of the explosion or• differences in the explosion energies
Isotopes of Ni and other elements• conversion of -
rays and positrons into heat and optical photons
Diehl and Timmes (1998)
Radioactivity
Contardo (2001)
Bolometric light curves
Stritzinger
Ni masses from light curves
Stritzinger
Ejecta masses from light curves
γ-ray escape depends on the total mass of the ejecta
v: expansionvelocity
κ: γ-ray opacity
q: distributionof nickel
q
vvt
qM ej
222
0
8
Stritzinger et al. 2006
Ejecta masses
Large range in nickel and ejecta masses• no ejecta mass at 1.4M
• factor of 2 in ejecta masses• some rather smalldifferences betweennickel and ejectamass
Stritzinger et al. 2006
Type Ia SupernovaeIndividual explosions
• differences in explosion mechanism– deflagration vs. delayed detonations
• 3-dimensional structures– distribution of elements in the ejecta– high velocity material in the ejecta
• explosion energies– different expansion velocities
• fuel– amounts of nickel mass synthesised
• progenitors– ejecta masses?
Standard SNe Ia?
What is the definition of a normal SN Ia?• light curves
– already used to normalise the peak luminosity– second parameter
– SALT2 Guy et al.– CMAGIC Wang et al.
• expansion velocities– observational coverage (spectroscopy!)
• spectral twins– observational coverage (spectroscopy!)
Reddening? K-corrections? Local velocity field? Evolution?
The importance of the local sample
All cosmological interpretations make use of the same local sample! Wood-Vasey et al. 2007
Blondin 2005
All SNe Ia from Tonry et al. 2003
Three highest-z objects removed
Only objects with 0.2<z<0.8
The importance of the local sample
Systematics of the local sample could be a problem (local impurities in the expansion field, e.g. ‘Hubble bubble’)
Jha et al. 2007
Where does the Hubble flow begin?Haugbølle et al. 2007
Is the Hubble Bubble real?
Jha et al. (2007) confirm earlier results • Riess et al. (1996), Zehavi et al. (1998)
Claimed to be a colour effect
Conley et al. (2007), Wang (2008)
use of a non-standard reddening law ‘removes’ the Hubble Bubble
Conley et al. 2007
Reddening
Standard reddening?• indications from many SNe Ia that RV<3.1
– e.g. Krisciunas et al., Elias-Rosa et al.
• free fit to distant SNe Ia gives RV≈2– Guy et al., Astier et al.
• Hubble bubble disappears with RV≈2– Conley et al., Wang
Need good physical understanding for this!
Where are we …
ESSENCECFHT Legacy Survey
Higher-z SN Search(GOODS)
SN FactoryCarnegie SN ProjectSDSSII
SNAP/LSST
Plus the local searches:LOTOSS, CfA, ESC
The SN Ia Hubble Diagram
Combination of ESSENCE, SNLS and nearby SNe Ia
Wood-Vasey et al. 2007
First cosmology results published
SNLS• Astier et al. 2006 – 71 distant SNe Ia• various papers describing spectroscopy (Lidman et al.
2006, Hook et al. 2006), rise time (Conley et al. 2006) and individual SNe (Howell et al. 2006)
ESSENCE• Wood-Vasey et al. 2007 – 60 distant SNe Ia• Miknaitis et al. 2007 – description of the survey• Davis et al. 2007 – comparison to exotic dark energy
proposals• spectroscopy (Matheson et al. 2005, Blondin et al. 2006)
Cosmology resultsSNLS 1st year (Astier et al. 2006)
• 71 distant SNe Ia – flat geometry and combined with BAO results
ΩM = 0.271 ± 0.021 (stat) ± 0.007 (sys) w = -1.02 ± 0.09 (stat) ± 0.054 (sys)
ESSENCE 3 years (Wood-Vasey et al. 2007)• 60 distant SNe Ia
– plus 45 nearby SNe Ia, plus 57 SNe Ia from SNLS 1st year
– flat geometry and combined with BAO w = -1.07 ± 0.09 (stat) ± 0.13 (sys) M = 0.27 ± 0.03
The currently most complete SN Ia sample
(Riess et al. 2007)
Collected all available distant SNe Ia• Riess et al. (2004)• Astier et al. (2006)• Wood-Vasey et al. (2007)
23 SNe Ia with z>1 total of 182 SNe Ia with z>0.0233
(v=7000 km/s)lower redshift limit to avoid any local effects
SN Ia Hubble Diagram
Riess et al. 2007
Check for acceleration, i.e. H(z)(model independent!)
Analysis
Riess et al. 2007
Analysis
Reconstruct w(z) from the data following Huterer & Cooray (2005):
Construct ‘independent’ redshift bins at 0.25, 0.70 and 1.35 and compare w(z)
weak priorstrongest prior
Riess et al. 2007
flat ΛCDM
variable ω
Comparison to other models
DGP model
Davis et al. 2007
standard Chaplygin gas
The next steps( Goobar, Mörtsell)
At the end of 2008• about 1000 SNe Ia for cosmology• constant ω determined to 5%• accuracy dominated by systematic effects
– reddening, correlations, local field, evolution
Test for variable ω• required accuracy ~2% in individual distances• can SNe Ia provide this?
– can the systematics be reduced to this level?– homogeneous photometry?– handle 10000 SNe Ia?
Time variable ω?
Wood-Vasey et al. 2007w0
wa
Riess et al. 2007
Requirements
Limit uncertainties to below 2%• solve the local field problem (Haugbølle)• solve reddening problem• understand evolution ( Davis, Smith)
– amongst SNe Ia (e.g. metallicity effects)– within the sample (e.g. correlations)
• understand SN Ia physics ( Stritzinger)– progenitors– explosion mechanism(s)– 3-dimensional
Sullivan et al. 2006
Unexplored territorySN Ia physics
• UV and thermal IR• earliest phases• very late phases• colour evolution• ‘tomography’• signatures of the progenitors
Cosmology• z>1