Baryon Acoustic Oscillations

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Baryon Acoustic Oscillations
2009/01/14 ?????????????? _at_???

• Atsushi Taruya
• (RESCEU, Univ.Tokyo)

RESCEURESearch Center for the Early Universe
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Contents
Baryon acoustic oscillation and cosmology
BAO measurement with WFMOS
Activity of Japan BAO theory group
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Baryon Acoustic Oscillation (BAO)

• Acoustic oscillations of primeval baryon-photon
  fluid
• imprinted on the clustering of large-scale
  structure

Typical size
z

• Detection Observation of BAOs

SDSS main, LRG samples
2dF GRS
Eisenstein et al. 2005 Cole et al.2005 Hutsui
2006 Percival et al. 2007 Okumura et al. 2008
Cabre et al. 2008 Gaztanaga et al. 2008
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Observations of BAOs
Percival et al. (2007)
Eisenstein et al.(2005)
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Physics of BAOs brief sketch
380,000 year after the Big-Bang
BAO was imprinted around the time of decoupling
of photons from matter
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Characteristic Scale of BAOs
Sound horizon scale at the time of decoupling
(c.f. type Ia SNe )

• Physics of BAOs is well-known, unambiguous

• Insensitive to the presence of dark energy

(Only weakly depends on matter and baryon density
parameters)

• Theres no significant disturbances that erase
  acoustic patterns

BAO scale is a robust standard ruler
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Measuring Expansion History
Angular diameter distance
Redshift z
In addition, Hubble parameter of distant objects,
H(z), can be measured through Alcock Paczynski
effect.
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Current Status
Combined with WMAP5 results
-1.11 lt w lt -0.86 (95 CL)
-0.0175 lt K lt 0.0085 (95 CL).
Komatsu et al. (2008)
Flat prior
(WK)
w
curvature parameter
(WDE)
Dark energy density parameter
Dark energy E.O.S parameter
(w )
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Future BAO Measurement
Narrowing constraints on dark energy
A percent-level determination of H(z) DA(z)
SDSS LRG
Minimal requirement
2dF GRS
Planned WFMOS survey (z1 3) satisfies this
requirement, and
is complementary to other BAO experiments (BOSS,
HETDEX, )
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Toward Precision Measurement
Precision measurement of BAOs needs
accurate theoretical templates for P(k) and x(r)
in order to determine the BAO scale
Systematic effects on BAOs
Non-linear gravitational evolution
Redshift-space distortion
small, but non-negligible effects at percent level
Galaxy biasing
Development of theoretical modeling and
feasibility study for precision measurement
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Japan BAO Theory Group
(friends ?)
IPMU
I.Kayo, M.Takada, N.Yoshida
Univ. Tokyo
T.Hiramatsu (ICRR), T.Nishimichi, S.Saito,
Y.Suto, A.Taruya
NAOJ
T.Hamana, A.Nishizawa
Nagoya Univ.
T.Matsubara, N.Sugiyama, R.Takahashi
Hiroshima Univ.
H.Nomura, K.Yamamoto
People who are interested in BAO are very welcome
!!
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Publications
Yamamoto et al. 2006, PRD 74, 063525
Yamamoto et al. 2007, PRD 76, 023504
Nishimichi et al. 2007, PASJ 59, 1049
Matsubara 2008, PRD 77, 063530
Taruya Hiramatsu 2008, ApJ 674, 617
Saito, Takada Taruya 2008, PRL 100, 191301
Matsubara 2008, PRD 78, 083519
Takahashi et al. 2008, MNRAS 389, 1675
Nomura, Yamamoto Nishimichi 2008, JCAP 10, 031
Nishimichi et al. 2009, PASJ, in press
(arXiv0810.0813)
Takahashi et al. 2009, in prep.
Taruya et al. 2009, in prep.
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Modeling Non-linear Evolution

• Development of new analytic treatment
• based on perturbation theory

• Reduction of numerical systematics in N-bosy
  simulations

• Check of convergence regime of
• N-body simulations and analytic models

Accurate and reliable template for BAOs
(1 precision)

• Error forecast including non-Gaussian error is
  also developed.

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Modeling Non-linear Evolution
Real space
P(k)/Psmooth(k)
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Modeling Non-linear Evolution
Redshift space
(monopole)
x(r)
z0.5
P(k)/Psmooth(k)
1
2
z3
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Feasibility
Distance estimation error
Improved PT valid
DD/D
Improved PT valid
kmax h/Mpc
Nishimichi et al. (2009)
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Summary
Measurement of BAOs with future redshift surveys
opens a new window to probe cosmic expansion
history

• Acoustic signature of primeval baryon-photon
  fluid

can be used as cosmic standard ruler

• Measurement of BAOs leads to Simultaneous
  determination

of
(1 precision in WFMOS)
Nature of dark energy (equation-of-state
parameter)
Test of general relativity / cosmological
principle
Japan BAO theory group seriously considers BAO
experiment with WFMOS. Theoretical tools are now
developing.