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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.

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Baryon acoustic oscillations
Baryon Acoustic Oscillations

Renée Hlozek

Bruce Bassett

YabebalFantaye, Jacques Kotze


Baryon acoustic oscillations1
Baryon Acoustic Oscillations

Eisenstein 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 birth of cosmic ripples

  • 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.

The Birth of Cosmic Ripples

RECOMBINATION

Eisenstein


The birth of cosmic ripples1
The Birth of Cosmic Ripples

Following a pebble in the cosmic pond…

PHOTON DENSITY

MASS PROFILE

BARYON DENSITY

White & Eisenstein


The birth of cosmic ripples2
The Birth of Cosmic Ripples

PHOTON DENSITY

MASS PROFILE

BARYON DENSITY

The dark matter is slow to move – it only interacts gravitationally

White & Eisenstein


The birth of cosmic ripples3
The Birth of Cosmic Ripples

PHOTON DENSITY

MASS PROFILE

BARYON DENSITY

Photons and baryons move outward together, the radius of the shell moving at

White


The birth of cosmic ripples4
The Birth of Cosmic Ripples

z=1081: just before decoupling

PHOTON DENSITY

MASS PROFILE

BARYON DENSITY

The dark matter begins to follow the baryons

White


The birth of cosmic ripples5
The Birth of Cosmic Ripples

PHOTON DENSITY

MASS PROFILE – PHOTONS and BARYONS only

BARYON DENSITY

Lack of pressure support `freezes’ the radius of oscillation into baryon density

White


The birth of cosmic ripples6
The Birth of Cosmic Ripples

PHOTON DENSITY

MASS PROFILE – PHOTONS and BARYONS only

BARYON DENSITY

White


The birth of cosmic ripples7
The Birth of Cosmic Ripples

PHOTON DENSITY

MASS PROFILE

BARYON DENSITY

Dark matter continues to move slowly – towards baryon peak

White


The birth of cosmic ripples8
The Birth of Cosmic Ripples

PHOTON DENSITY

MASS PROFILE

BARYON DENSITY

Dark matter distribution now clusters around baryon peak.

White


The cosmic ruler
The Cosmic RULER

  • Final density profile peaks at r = 0 - with a second peak ata distance that depends on Ωm and h.

  • This is the baryon acoustic peak


Distance and expansion
Distance and Expansion

transverse

radial


Many pebbles in the pond
Many pebbles in the pond

  • But in reality there are superimposed rings of power

Bassett and RH, 2008


Enemies of the bao
Enemies of the BAO

Shot Noise

Bassett and RH, 2008


Enemies of the bao1
Enemies of the BAO

Cosmic Variance

Bassett and RH, 2008

We need lots of galaxies (N > 106) and large volume (V > 0.5 h-3Gpc3)


Ska bao
SKA BAO

Blake et al. 2005



Ska de constraints
SKA DE Constraints

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. 108vs109 galaxies – how much does that affect dark energy 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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