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Baryon Acoustic Oscillations. Renée Hlozek. Bruce Bassett Yabebal Fantaye , Jacques Kotze. Baryon Acoustic Oscillations. Eisenstein et al. 2005. Tegmark et al. 2005. Who will detect the BAO in the radio ?. MeerKAT may be the first. - PowerPoint PPT Presentation
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BARYON ACOUSTIC OSCILLATIONS
RENÉE HLOZEKBruce BassettYabebal Fantaye, Jacques Kotze
Baryon Acoustic OscillationsEisenstein et al. 2005 Tegmark et al. 2005
Who will detect the BAO in the radio?
MeerKAT may be the first.
Need to be ready to do the analyses before the telescope is operational
useful to review the key ideas.
It should!
SKA will provide stunning BAO constraints.
review the BAO forecasts for the SKA using Fisher4Cast.
The Universe is neutral.
Photons free-stream away
- no longer interact with ions.
Pressure support is removed.
Baryon wave stalls.
The Universe is ionized.
Photons and ions interact via Thomson scattering.
Perturbations in the cosmic plasma oscillate as acoustic waves.
R
ECOM
BINA
TION
Eisenstein
The Birth of Cosmic Ripples
The Birth of Cosmic RipplesFollowing a pebble in the cosmic pond…
White & Eisenstein
PHOTON DENSITYBARYON DENSITY MASS PROFILE
The Birth of Cosmic Ripples
The dark matter is slow to move – it only interacts gravitationally
PHOTON DENSITYBARYON DENSITY MASS PROFILE
White & Eisenstein
The Birth of Cosmic Ripples
White
Photons and baryons move outward together, the radius of the shell moving at
)4/31(3 b
cv
PHOTON DENSITYBARYON DENSITY MASS PROFILE
The Birth of Cosmic Ripples
White
The dark matter begins to follow the baryons
z=1081: just before decoupling
PHOTON DENSITYBARYON DENSITY MASS PROFILE
The Birth of Cosmic Ripples
White
PHOTON DENSITYBARYON DENSITY MASS PROFILE – PHOTONS and BARYONS only
Lack of pressure support `freezes’ the radius of oscillation into baryon density
The Birth of Cosmic Ripples
White
PHOTON DENSITYBARYON DENSITY MASS PROFILE – PHOTONS and BARYONS only
The Birth of Cosmic Ripples
White
PHOTON DENSITYBARYON DENSITY MASS PROFILE
Dark matter continues to move slowly – towards baryon peak
The Birth of Cosmic Ripples
White
PHOTON DENSITYBARYON DENSITY MASS PROFILE
Dark matter distribution now clusters around baryon peak.
The Cosmic RULERFinal density
profile peaks at r = 0 - with a second peak at a distance that depends on Ωm and h.
• This is the baryon acoustic peak
Mpctzc 130~26.3/000,4001100~)1(~
Distance and Expansion
radial
transverse
• But in reality there are superimposed rings of power
Many pebbles in the pond
Bassett and RH, 2008
Enemies of the BAOShot Noise
Bassett and RH, 2008
Enemies of the BAOCosmic Variance
We need lots of galaxies (N > 106) and large volume (V > 0.5 h-3Gpc3)Bassett and RH, 2008
SKA BAO
Blake et al. 2005
Intuitive ERROR ELLIPSES
Fisher4Cast
Two key questions:
What is the best HI survey for the SKA?
How much would a 50% or 20% SKA lose in terms of dark energy?
For e.g. 108 vs 109 galaxies – how much does that affect dark energy constraints?
SKA DE Constraints
www.cosmology.org.za• Open source, modular and battle-tested GUI designed using software engineering principles
• Approximately 400 downloads since May 2008
• Planned Extensions: lensing, CMB, direct radio survey support
• Encourage Collaboration and Extensions
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