probing dark energy with cosmological observations
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Probing Dark Energy with Cosmological Observations. Fan, Zuhui ( 范祖辉 ) Dept. of Astronomy Peking University. Outline Introduction Cosmological Probes Current Status Future. Introduction The development of cosmology is - PowerPoint PPT PresentationTRANSCRIPT
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Probing Dark Energy with Cosmological Observations Fan, Zuhui ( 范祖辉 ) Dept. of Astronomy Peking University
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Outline
Introduction Cosmological Probes Current Status Future
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Introduction
The development of cosmology is driven by observations
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The universe is expanding ( ) – Big Bang
Hubble
0
R
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The expansion is accelerating ( ) (1998, 1999)
0
R
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Standard cosmological scenario: Einstein’s equations govern the evolution of the universe
R: scale factor of the universe
ii
GRk
RR
38
22
2
)3(3
4i
ii pG
RR
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Normal matter:
The accelerating universe calls for the existence of dark energy with negative pressure
0
R
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Understanding the nature of dark energy Theoretical physics: dark energy models Cosmology: extract constraints on dark energy from different observations
w=-1? w=constant? w(z) ?
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Cosmological probes on dark energy
Global properties of the universe Geometry and expansion history of the
universe
Dynamical evolution of the large-scale structure of the universe
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Expansion of the universe: SNe Ia: standard candle luminosity distance
Clusters of galaxies: SZ+X-ray angular diameter distance
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Geometry of the universe: CMB: angular positions of the sound peaks sensitive to the total matter content
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Dynamical evolution of the universe Large-scale structure of the universe galaxy redshift surveys power spectrum correlation function
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detection of acoustic peak from the SDSS LRG sample
Eisenstein et al. astro-ph/0501171
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Dark energy dependence
growth factor of density perturbations Cosmological distortion: AP test
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The formation and evolution of clusters of galaxies abundance evolution: density growth volume element
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gas fraction in clusters of galaxies assume the gas fraction fgas(z) invariant constraints on cosmology (dA(z) – z relation)
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Gravitational lensing strong lensing weak lensing dynamical evolution of density perturbations angular diameter distances to the source, to the lens, and from lens to the source
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Current status SNe Ia (Riess et al. 2004 astro-ph/0402512 ApJ, 607, 665)
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Dark energy constraints
equation of state constant w
)(zwp
13.019.002.1 w 20.0
18.008.1 w
%)95(46.178.0 w
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w(z) zwww '0
22.028.00 31.1 w 81.0
90.0' 48.1 w
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Lyα+galaxy bias+SNe+CMB (Seljak et al. 2004, astro-ph/0407372, PRD, 71, 103515 (2005)) constant w
99.0w
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)1/(1,)1()1( 22
10 zawawaww
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cluster gas fraction +CMB+SN (Rapetti et al. MNRAS, 360, 555 (2005))
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equation of state aett
tet wwwzzzwzww
00 ,
44.062.0
33.039.00 66.0,27.1
etww
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weak lensing (M. Jarvis et al. astro-ph/0502243) CTIO lensing survey: 75 deg2, 19<R<23, 2*106 gal
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dark energy constraint
constant w .).%95(894.0 156.0208.0 lcw
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w(a)
the second peak corresponds to w(a=0)~1
not physically relevant
)1()( 0 awwaw a
.).%95(31.1,19.1 04.340.2
53.074.10 lcww a
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As of today:
w=-1 (cosmological constant) is consistent
with all the observational data available to us
Slightly favor w<-1
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Future SNe Ia SNAP Supernova/Acceleration Probe
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Dark energy constraints
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SNAP: weak lensing surveyDeep survey: 15 deg2, 250/arcmin2Wide survey: 300-1000 deg2 100/arcmin2Panoramic survey: 10000 deg2 40-50/acrmin2
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Equation of state
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CMB: Planck standard ruler: sound horizon baryon wiggles in matter power spectrum determination of other parameters Ωtotal, σ8, Ωm, Ωb, … ISW
Large-scale structure: LAMOST
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LAMOST galaxy redshift survey (Sun, Su and Fan 2005) three redshift bins centered at 0.3, 0.4, and 0.5 distant observer approximation
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With bins of higher redshifts, the constraints can be improved
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Without distant-observer approximation z=0.2-0.4
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a
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Parameterization Priors systematic errors