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