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. 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 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 Ripples Following a pebble in the cosmic pond… BARYON DENSITY PHOTON DENSITY MASS PROFILE White & Eisenstein

The Birth of Cosmic Ripples BARYON DENSITY PHOTON DENSITY MASS PROFILE The dark matter is slow to move – it only interacts gravitationally White & Eisenstein

The Birth of Cosmic Ripples BARYON DENSITY PHOTON DENSITY MASS PROFILE Photons and baryons move outward together, the radius of the shell moving at White

The Birth of Cosmic Ripples z=1081: just before decoupling BARYON DENSITY PHOTON DENSITY MASS PROFILE The dark matter begins to follow the baryons White

The Birth of Cosmic Ripples BARYON DENSITY PHOTON DENSITY MASS PROFILE – PHOTONS and BARYONS only Lack of pressure support `freezes’ the radius of oscillation into baryon density White

The Birth of Cosmic Ripples BARYON DENSITY PHOTON DENSITY MASS PROFILE – PHOTONS and BARYONS only White

The Birth of Cosmic Ripples BARYON DENSITY PHOTON DENSITY MASS PROFILE Dark matter continues to move slowly – towards baryon peak White

The Birth of Cosmic Ripples BARYON DENSITY PHOTON DENSITY MASS PROFILE Dark matter distribution now clusters around baryon peak. White

The Cosmic RULER Final 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

Distance and Expansion transverse radial

Many pebbles in the pond But in reality there are superimposed rings of power Bassett and RH, 2008

Enemies of the BAO Shot Noise Bassett and RH, 2008

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 Blake et al. 2005

Intuitive ERROR ELLIPSES Data should all be the same – don’t regenerate new data. Try the panels side side Fisher4Cast

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. 108 vs 109 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