Type Ia Supernovae and Dark Energy · Type Ia Supernovae (together with additional information on...
Transcript of Type Ia Supernovae and Dark Energy · Type Ia Supernovae (together with additional information on...
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Type Ia Supernovae andDark Energy
Bruno Leibundgut
European Southern Observatory
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Outline
The Hubble diagram of Type Ia Supernovae• evidence for accelerated expansion
• evidence for/against dust and evolution
Systematics of Type Ia Supernovae
Measuring the equation of state parameter
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Riess et al. (2003)
Higher-z SN team (GOODS/HST)
Distant supernovae
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The principle
Establish a cosmological distance indicatorin the local universe (z<0.05)e.g. Cepheids, SNe II, Tully-Fisher relation,fundamental plane relation, surfacebrightness fluctuations, SNe Ia)
Measure objects at cosmological distances establish identity of distance indicator control measurement errors
evolution (primary and secondary)interstellar and intergalactic dustgravitational lensing
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Type Ia Supernovae
Establish a cosmological distance indicatorin the local universe (z<0.05)Type Ia Supernovae can be normalisedthrough their light curve shapes (102 objects)Ëexcellent relative distances (Phillips 1993, Hamuy et al.
1996, Riess et al. 1996, 1998, 1999, Perlmutter et al. 1997, Phillipset al. 1999, Suntzeff et al. 1999, Jha et al. 1999, 2003)
Measure objects at cosmological distances 77 distant SNe Ia (0.3<z<1.0) published
(Garnavich et al. 1998, Riess et al. 1998, Perlmutter et al. 1997,1999, Tonry et al. 2003, Suntzeff et al. 2004, Barris et al. 2004,Leibundgut et al. 2004)
evolution Ë light curve shapes, colours, spectroscopy
dust Ë colours, spectroscopy
gravitational lensing Ë difficult, need mapping oflight beam
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The nearby SN Ia sample
Evidence for gooddistances
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Starting from Einstein’s Fieldequation
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Friedmann cosmologyAssumption:homogeneous and isotropic universe
Null geodesic in a Friedmann-Robertson-Walker metric:
[ ]Ô
Ô˝¸
ÔÓ
ÔÌÏ
¢W+¢+W+¢+WWW
+=
-
LÚ zdzzSH
czD
z
ML
21
0
32
0
)1()1()1(
kk
k
MM H
Gr
p203
8=W
20
2
2
HR
kck -=W
20
2
3H
cL=WL
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Cosmology inthe Hubble
diagram
Assumption:Lambda is constantNo time-dependence inthe equation of state
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Tonry et al. 2003
Supernovacosmology
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Mean distancebetween galaxies
today
fainter
redshift
WM = 1
Time
Closed WM > 1
Open WM < 1
WM = 0
- 14 - 9 - 7
billion years
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Perlmutter 2003
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Distant SNe IaDistant objects appearfainter than theirnearby counterpartsThis is a 3.5s result(High-z SN Team andSupernova CosmologyProject)
• evolution
• dust
• cosmology
Checks:
Dust• observations over many
filters
Evolution• spectroscopy
Cosmology• more distant SNe Ia
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Is dust a problem?
Falco et al. 1999
Leibundgut 2001
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SNe Ia in elliptical galaxiesDetermination of host galaxy morphologies
• 38 SNe Ia from the SCP sample
Sullivan et al. 2003
Elliptical galaxiesare dust-free
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Modified Hubble diagram
Supernova Cosmology Project Sample
Sullivan et al. (2003)
WM=0.28; WL=0.72
Sullivan et al. 2003
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Leibundgut and Sollerman 2001
Evolution?Spectroscopy ofdistant SNe Ia
Coil et al. 2000
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Evolution? - Colours
Leibundgut 2001
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209 SNe Ia inone diagram
Tonry et al. 2003
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209 SN Ia and mediansTonry et al. 2003
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79 SNe Ia
Cosmology
Leibundgut 2001
H0=63 km s-1 Mpc-1
Tonry et al. 2003
155 SNe Ia
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SN Ia and 2dF constraints
KP:h = 0.72 ± 0.08
2dF:WM=0.2±0.03
Tonry et al. 2003
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2dF:WM=0.2±0.03
KP:h = 0.72 ± 0.08
Tonry et al. 2003
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Supernovae
Extremely bright stellar explosions
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SN Ia Systematics?
Explosions not fully understood• many possible models
– Chandrasekhar-mass models
– deflagrations vs. detonations
Progenitor systems not known• white dwarfs yes, but …
– double degenerate vs. single degenerate binaries
Ë Evolution very difficult to control
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B
V
I
The SN Ia luminositycan be normalised
Bright = slow Dim = fast
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Nature of the Dark Energy?
Currently two proposals:• cosmological constant
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Nature of the Dark Energy?
Currently two proposals:• cosmological constant
• quintessence– decaying particle field
– signature:– equation of state parameter with
2c
p
rw =1-≠w
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On to new physics?
Both quintessence and the cosmologicalconstant would require additions beyondthe current standard model of physics.
Type Ia Supernovae (together withadditional information on _M) candistinguish between those twopossibilities• required is a large homogeneous set (about
200) of distant (0.2 < z < 0.8) supernovae
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General luminosity distance
• with and
wM= 0 (matter)
wR= _ (radiation)
wL= -1 (cosmological constant)
Ô
Ô˝¸
ÔÓ
ÔÌÏ
¢˙˚
˘ÍÎ
È¢+W+¢+WW
W
+=
-
+Ú Â zdzzSH
czD
z
iiL
i
21
0
)1(32
0
)1()1()1( w
kk
k
 W-=i
i1k2c
p
i
ii r
w =
The equation of state parameter w
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w
Garnavich et al. 1998
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SN Ia and 2dF constraints
KP:h = 0.72 ± 0.08
Quintessence
Cosmic strings
Cosmological constant
2dF:W M h = 0.2 ± 0.03
Tonry et al. 2003
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%)95(73.0-<w
Tonry et al. 2003
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ResultsSupernovae measure distances over a large
cosmological rangeThey are complementary to the CMB
measurements in that they can measurethe dynamics of the cosmic expansion
Ë map the cosmological expansion• SNe Ia indicate accelerated expansion for the
last 6 Gyr• There are indications that the accelerations
turns into a deceleration at z>1 (>8 Gyr)• dynamic age of the universe H0t0=0.95±0.04
(13 Gyr for H0=72 km s-1Mpc-1; 15 Gyr for H0=64 km s-1Mpc-1)
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It’s not all doneyet …
Tonry et al. 2003
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GOODS (Higher-z) Supernovae
Find supernovae atz>1.2 from the GOODSACS observations
Riess et al. (2003)
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GOODS SupernovaeVLT spectrumFORS2 - 300I - 3.5h integration (6. Nov ‘02)
Ca II H&Kz=1.31
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Summary (Problems)
Supernova systematics• unknown explosion mechanism
• unknown progenitor systems
• light curve shape correction methods for theluminosity normalisation (SCP vs. HZT)
• signatures of evolution in the colours?
• spectroscopy?
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The Future
Future experiments will distinguishbetween a cosmological constant orquintessence• ESSENCE, CFHT Legacy Survey, VST,
VISTA, NGST, LSST, SNAP
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The Future
Future experiments will distinguishbetween a cosmological constant orquintessence• ESSENCE, CFHT Legacy Survey, VST,
VISTA, NGST, LSST, SNAP
Systematic uncertainties depend on ourunderstanding of the supernovae• nearby samples, explosion models, radiation
hydrodynamics
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Einstein’s cosmological constantCan not be explained within the currentparticle physics models
QuintessenceSignatures of higher dimensions
some theories of gravity work in higherdimensions - leakage from there into the 4-dimensional world would effect theFriedmann equation
Phantom energieDark energy will tear the universe apart(Big Rip)
Interpretations/Speculations
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Summary
Only Type Ia supernovae can currentlyprovide a possible answer to what theDark Energy is:• what is _?
• what is d_/dt?
• what is the future of the universe?