Title: Measuring the equation of state with highredshift supernovae
1Measuring the equation of state with
high-redshift supernovae
- Bruno Leibundgut
- European Southern Observatory
2Supernova classification
SN II (H) SN Ib/c (no H/He) Hypernovae/GRBs
SN Ia (no H)
3Supernova Spectroscopy
Type II
4SupernovaSpectroscopy
Type Ia
5Supernova classification
SN II (H) SN Ib/c (no H/He) Hypernovae/GRBs
SN Ia (no H)
6Supernova types
- thermonuclear SNe
- from low-mass stars (lt8M?)
- highly evolved stars (white dwarfs)
- explosive C and O burning
- binary systems required
- complete disruption
- core-collapse SNe
- high mass stars (gt8M?)
- large envelopes (still burning)
- burning due to compression
- single stars (binaries for SNe Ib/c)
- neutron star
7Energy sources
- gravity ?Type II supernovae
- collapse of a solar mass or more to a neutron
star
8Energy sources
- gravity ?Type II supernovae
- collapse of a solar mass or more to a neutron
star - release of 1053 erg
- mostly ?e
- 1051 erg in kinetic energy (expansion of the
ejecta) - 1049 erg in radiation
- nuclear (binding) energy ? Type Ia
- explosive C and O burning of about one solar mass
- release of 1049 erg
9- Core-collapse supernovae
- SN 1987Athe best observed supernova ever
Suntzeff (2003)
10Classification
Supernovae in Garching D. Baade, R. Diehl, R.
Gilmozzi, W. Hillebrandt. H.-Th. Janka, K. Kjær,
R. Kotak, P. Mazzali, E. Müller, A.
Pastorello, F. Patat, R. Röpke, S. Taubenberger,
S. Valenti
11Type Ia Supernovae
- Explosion physics relatively well understood
- significant progress in the past decade
(especially at MPA) - Radiation transport remains a big problem
- simplifications can provide new insight into the
explosion models - progress in the ab initio calculations as well
- however, missing information in the atomic
transitions
12Thermonuclear Supernovae
The standard model
White dwarf in a binary
system Growing to the Chandrasekhar mass
(MChand1.4 M?) by mass transfer from a nearby
star
13The standard model
- Explosion energy
- Fusion of
- CC, CO, OO
- ? "Fe
He (H) from binary companion
CO, M Mch
Density 109 - 1010 g/cm Temperature a
few 109 K Radii a few 1000 km
There is a lot more to this you need to contact
your friends at the MPA (W. Hillebrandt, F.
Röpke, et al.)
14Global 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
15Radioactivity
- Isotopes of Ni and other elements
- conversion of ?-rays and positrons into heat and
optical photons
Diehl and Timmes (1998)
16Bolometric light curves
17Ni masses from light curves
18Are SNe Ia standard candles?
- No!
- large variations in
- light curve shapes
- colours
- spectral evolution
- polarimetry (Baade, Patat)
- some clear outliers
- what is a type Ia supernova?
- differences in physical parameters
- Ni mass
- ejecta mass
19The expansion of the universe
- Luminosity distance in an isotropic, homogeneous
universe as a Taylor expansion
20The nearby SN Ia sample and Hubbles law
Evidence for good distances
21Are SNe Ia good distance indicators?
- Yes!
- normalisation through the light curve shape
- still problems with methods!
- Hubble diagram of nearby SNe Ia
- peak luminosities of nearby supernovae
22SN Projects
SN Factory Carnegie SN Project SDSSII
ESSENCE CFHT Legacy Survey
Higher-z SN Search (GOODS)
SNAP/LSST
23Determining H0 from models
- Hubbles law
- Luminosity distance
- Ni-Co decay
24H0 from the nickel mass
a conversion of nickel energy into radiation
(LaENi) e(t) energy deposited in the supernova
ejecta
Stritzinger Leibundgut (2005)
25H0 and the Ni mass
- Individual SNe follow the 1/M
- dependency.
- Problem
- Since they have individual Ni masses it is not
clear which one to apply!
26Determine a lower limit for H0
27Acceleration
- Originally thought of as deceleration due to the
action of gravity in a matter dominated universe
28(No Transcript)
29Friedmann cosmology
Assumption homogeneous and isotropic
universe Null geodesic in a Friedmann-Robertson-W
alker metric
30Measure acceleration
31Cosmological implication
- Empty Universum
- Einstein de Sitter
- Lambda-dominatedUniverse
- Concordance Cosmology
32Adding jerk
Riess et al. 2004
33The equation of state parameter ?
- General luminosity distance
- with and
- ?M 0 (matter)
- ?R ? (radiation)
- ?? -1 (cosmological constant)
34For a flat universe this should be possible
35ESSENCE
- World-wide collaboration to find and characterise
SNe Ia with 0.2 lt z lt 0.8 - Search with CTIO 4m Blanco telescope
- Spectroscopy with VLT, Gemini, Keck, Magellan
- Goal Measure distances to 200 SNe Ia with an
overall accuracy of 5 ? determine ? to 10
overall
36SNLS The SuperNova Legacy Survey
World-wide collaboration to find and characterise
SNe Ia with 0.2 lt z lt 0.8 Search with CFHT 4m
telescope Spectroscopy with VLT, Gemini, Keck,
Magellan Goal Measure distances to 1000 SNe Ia
with an overall accuracy of 5 ? determine ? to
7 overall
37First 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)
38Caveat
- All cosmological interpretations make use of the
same 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
39All SNe Ia from Tonry et al. 2003
Three highest-z objects removed
Only objects with 0.2ltzlt0.8
Blondin 2005
40ESSENCE spectroscopy
Matheson et al. 2005
41A slow, long process
- ESSENCE will observe one more year (2007)
- SNLS will reach more than 500 SNe Ia by 2007/8
42Spectroscopic study
Blondin et al. 2006
43The ESSENCE Hubble Diagram
- Combination of ESSENCE, SNLS and nearby SNe Ia
44SNLS 1st year results
Astier et al. (2006)
- Based on 71 distant SNe Ia
- for a flat ?CDM cosmology
- OM0.2640.042 (stat) 0.032 (sys)
- Combined with BAO (Eisenstein et al. 2005)
- OM 0.271 0.021 (stat) 0.007 (sys)
- w -1.02 0.09 (stat) 0.054 (sys)
45ESSENCE cosmology results
- Based on 60 distant SNe Ia
- plus 45 nearby ones
- plus 57 SNLS first year SNe Ia (Astier et al.)
- Combined with BAO (Eisenstein et al. 2005)
- w-1.070.09(stat)0.13(sys) 162 incl. Astier et
al. sample - ?M0.270.03
- w-1.050.13(stat)0.13(sys) 102 SNe Ia only
ESSENCE - ?M0.270.03
- Systematics include differences in the absorption
law and selection effects due to the limiting
magnitude and the local expansion field
Miknaitis et al. (2007) Wood-Vasey et al. (2007)
46Systematics table
47Time variable ??
48New distant SNe
Riess et al. 2007
- Observations of 21 new SNe Ia
- HST/ACS search (2003-5) in CDF-S and HDF-N
NICMOS for follow-up - 0.36 lt z lt 1.4
- mostly 0.8ltzlt1.4
49SN Ia sample
- Collected all available distant SNe
- Riess et al. (2004)
- Astier et al. (2006)
- Wood-Vasey et al. (2007)
- ? 23 SNe Ia with zgt1
- ? total of 182 SNe with zgt0.0233 (v7000 km/s)
- lower redshift limit to avoid any local effects
(Hubble bubble)
50SN Ia Hubble Diagram
51Analysis
- Check for acceleration (model independent!)
- determine H(z)
- convert DL to comoving distance r(z)
- sort the SNe by redshift z and measure
- which is H-1(zi)
- and determine the expansion rate
52Analysis
- 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)
53Comparison to other models
Davis et al. 2007
54The SN Ia Hubble diagram
- Powerful tool to
- establish SNe Ia as good distance indicators
- measure the absolute scale of the universe (H0)
- determine the amount of dark energy
- measure the equation of state parameter of dark
energy - current best results are consistent with w-1
55Dark Energy
- Accelerating expansion of the universe appears
very safe by now - Time-variable ? will be difficult to determine,
unless another breakthrough in distance
determinations can be achieved - Current SN experiments find a ? consistent with a
cosmological constant