Measuring the equation of state with highredshift supernovae

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Measuring the equation of state with
high-redshift supernovae

• Bruno Leibundgut
• European Southern Observatory

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Supernova classification

• Based on spectroscopy

SN II (H) SN Ib/c (no H/He) Hypernovae/GRBs
SN Ia (no H)
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Supernova Spectroscopy
Type II
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SupernovaSpectroscopy
Type Ia
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Supernova classification

• Based on spectroscopy

SN II (H) SN Ib/c (no H/He) Hypernovae/GRBs
SN Ia (no H)
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Supernova 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

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Energy sources

• gravity ?Type II supernovae
• collapse of a solar mass or more to a neutron
  star

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Energy 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

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• Core-collapse supernovae
• SN 1987Athe best observed supernova ever

Suntzeff (2003)
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Classification
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
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Type 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

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Thermonuclear 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
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The 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.)
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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

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Radioactivity

• Isotopes of Ni and other elements
• conversion of ?-rays and positrons into heat and
  optical photons

Diehl and Timmes (1998)
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Bolometric light curves
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Ni masses from light curves
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Are 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

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The expansion of the universe

• Luminosity distance in an isotropic, homogeneous
  universe as a Taylor expansion

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The nearby SN Ia sample and Hubbles law
Evidence for good distances
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Are 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

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SN Projects
SN Factory Carnegie SN Project SDSSII
ESSENCE CFHT Legacy Survey
Higher-z SN Search (GOODS)
SNAP/LSST
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Determining H0 from models

• Hubbles law
• Luminosity distance
• Ni-Co decay

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H0 from the nickel mass
a conversion of nickel energy into radiation
(LaENi) e(t) energy deposited in the supernova
ejecta
Stritzinger Leibundgut (2005)
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H0 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!

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Determine a lower limit for H0
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Acceleration

• Originally thought of as deceleration due to the
  action of gravity in a matter dominated universe

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(No Transcript)
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Friedmann cosmology
Assumption homogeneous and isotropic
universe Null geodesic in a Friedmann-Robertson-W
alker metric
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Measure acceleration
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Cosmological implication

• Empty Universum
• Einstein de Sitter
• Lambda-dominatedUniverse
• Concordance Cosmology

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Adding jerk
Riess et al. 2004
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The equation of state parameter ?

• General luminosity distance
• with and
• ?M 0 (matter)
• ?R ? (radiation)
• ?? -1 (cosmological constant)

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For a flat universe this should be possible
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ESSENCE

• 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

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SNLS 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
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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)

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Caveat

• 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
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All SNe Ia from Tonry et al. 2003
Three highest-z objects removed
Only objects with 0.2ltzlt0.8
Blondin 2005
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ESSENCE spectroscopy
Matheson et al. 2005
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A slow, long process

• ESSENCE will observe one more year (2007)
• SNLS will reach more than 500 SNe Ia by 2007/8

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Spectroscopic study
Blondin et al. 2006
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The ESSENCE Hubble Diagram

• Combination of ESSENCE, SNLS and nearby SNe Ia

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SNLS 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)

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ESSENCE 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)
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Systematics table
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Time variable ??
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New 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

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SN 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)

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SN Ia Hubble Diagram
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Analysis

• 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

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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)

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Comparison to other models
Davis et al. 2007
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The 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

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Dark 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